HIGH GAIN AMPLIFIER WITH HIGH TRACKING SPEED

Abstract

Amplifier (10) with high gain and high tracking speed, comprising: a pair of input transistors (MNP 12, MNN 14) to which input voltages (IN+ and IN-) are applied; a pair of loads switched as diodes (MPP 16, MPN 18) connected to the input transistors (MNP 12, MNN 14); at least a pair of current sources (MPIP 20, MPIN 22) connected to the loads switched as diodes (MPP 16, MPN 18);and a bias control (28) designed to switch off the at least one pair of current sources (MPIP 20, MPIN 22) to enable a high tracking speed for the amplifier (10), wherein the bias control (28) switches off the current sources (MPIP 20, MPIN 22) during a coarse tracking mode of the amplifier (10) when the amplifier (10) is tracking, and to switch on the at least one pair of current sources (MPIP 20, MPIN 22) to enable a high gain for the amplifier (10), and wherein the bias control (28) switches on at least one pair of current sources (MPIP 20, MPIN 22) at the end of the tracking and leaves the current sources (MPIP 20, MPIN 22) switched on when the amplifier (10) is not tracking.

Description

TECHNICAL FIELD OF DISCLOSUREThe present disclosure relates generally to electrical circuits and, more particularly, to a method and apparatus for a high gain, high tracking speed amplifier.GENERAL STATE OF THE ARTDifferential amplifiers amplify (e.g., increase, increase, etc.) Differential signals (e.g., signals measured between two nodes as equal and opposite). The factor by which the signals are amplified, called the gain of the amplifier, is a measure of the ability of the amplifier to increase the power or amplitude of the signal from input to output. The gain is finite and depends on the frequency of the input signal. At low frequencies, the gain is maximum, it normally decreases exponentially with increasing frequency, and has a value of one at the frequency commonly referred to as the one-gain frequency. For an amplifier implemented with a given technology, the product of the amplifier's gain and maximum bandwidth is generally constant. Thus, the design of the amplifier typically involves a trade-off between high gain and wide bandwidth.If the input of the amplifier changes too fast, the output is slowed by the tracking speed of the amplifier, which is the maximum rate of change of the output voltage per unit time (e.g., expressed in volts per second). The change in output voltage over time for large input steps is generally referred to as "sliding" (tracking). The tracking speed of the amplifier generally decreases as the gain increases, resulting in an exchange relationship between gain and tracking speed (e.g., the higher the gain, the lower the tracking speed, and vice versa). High tracking speed is generally a desirable characteristic of the amplifier; likewise, high gain is also a desirable characteristic of the amplifier; however, amplifiers typically cannot be designed to provide both high tracking speed and high gain.One mechanism for achieving a high gain, high tracking speed amplifier involves adding a current feedforward circuit to a standard resistive load differential amplifier. The loop gain of the feedback circuit is designed to be less than one, and is controlled so as to ensure the stability of the entire unit. The load resistors are connected between a supply pole and the outputs of the differential amplifier and are connected in parallel to two current sources which connect their current feedback at the outputs. Another implementation of a high gain, high tracking speed amplifier includes a primary side amplifier in combination with a secondary side high power amplifier that is activated only in short periods of time when very high tracking speed is required.In yet another implementation, a buffer circuit having both high gain and high tracking speed is implemented using a high gain, low tracking speed amplifier and a switching network having three separate phases of operation. In the first phase, the output of the amplifier is disconnected from the load to allow the output voltage of the amplifier to reach its final voltage level more quickly (e.g., achieve a high tracking speed). In the second phase, the switching network interconnects the amplifier output line with the amplifier input line, where the amplifier drives the voltage at the input line of the load to a voltage substantially equal to the voltage of the input signal (e.g., achieving high gain). In the third phase, the switching network disconnects the amplifier from the load and connects the input line of the load to a ground potential source in order to quickly track the input line of the load to ground potential.The reference US 2007 / 0 115 048 A1 relates to an equalizer with controllable, variable offset voltages at its output. It discloses a circuit comprising a tunable differential amplifier having a tunable complex impedance acting as a filter. The tunable amplifier includes a pair of input transistors to which an input voltage is applied. It further comprises two tunable balanced loads in the form of diode-connected NMOS transistors connected to the two input transistors. The amplifier further comprises two transistors serving as current sources, which are connected to the input transistors and the tunable complex impedance in. At low frequencies of the input signal, a high complex impedance is realized, while at higher frequencies of the input signal, the impedance decreases. As the impedance decreases, the current of the current sources increases, which leads to an amplification of the output signal at the balanced loads.TIETZE, U.; SCHENK, Ch.; Semiconductor Circuit Technology. 9th Edition, 1989. S.150-153, ISBN 978-3-662-11942-6 describes the adjusted frequency response correction, slew rate.Against the background of the prior art, the object of the present disclosure is to provide an amplifier and a method, each of which is suitable for improving the prior art and in particular for achieving a high gain and a high tracking speed.The object is achieved by the features of the independent patent claims. The dependent claims each have optional developments of the invention.SUMMARYThe present disclosure generally relates to a method and apparatus for a high gain, high tracking speed amplifier. In one embodiment, a high gain, high tracking speed amplifier is provided and includes a pair of input transistors to which an input voltage is applied, a pair of diode connected loads coupled to the input transistors, at least one pair of current sources coupled to the diode connected loads, and a bias controller configured to turn off the at least one pair of current sources to enable a high tracking speed for the amplifier, and turn on the at least one pair of current sources to enable a high gain for the amplifier. In particular embodiments, the current sources include transistors, the bias controller controls a bias voltage to the current sources, and the bias voltage is driven to the supply voltage (V dd) or to ground (GND) to turn off the current sources.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a simplified circuit diagram illustrating an embodiment of a high gain, high tracking speed amplifier; FIG. 2 is a simplified circuit diagram illustrating another embodiment of the high gain, high tracking speed amplifier; FIG. 3 is a simplified circuit diagram illustrating example details of an embodiment of the high gain, high tracking speed amplifier; FIG. 4 is a simplified flow diagram illustrating example operations that may be associated with an embodiment of the high gain, high tracking speed amplifier; FIG. 5 is a simplified flow diagram illustrating other example operations that may be associated with an embodiment of the high gain, high tracking speed amplifier; FIG. 6 is a simplified flow diagram illustrating still other example operations that may be associated with an embodiment of the high gain, high tracking speed amplifier; and FIG. 7 is a simplified flow diagram illustrating still other example operations that may be associated with an embodiment of the high gain, high tracking speed amplifier.DESCRIPTION OF EMBODIMENTS OF THE DISCLOSUREFIG. 1 is a simplified block diagram illustrating a high gain, high tracking speed amplifier 10 in accordance with the present disclosure. The amplifier 10 includes input transistors MNP 12 and MNN 14 to which the input voltages IN+ and IN- are applied. MNP 12 and MNN 14 are connected to transistors MPP 16 and MPN 18, which effectively function as diode-connected loads. The use of diode-connected transistors as the active load provides a smaller gain, and diode-connected loads may consume voltage margin (thus creating an exchange relationship between output voltage, voltage gain, and input common-mode range); however, diode-connected loads have a small impedance and may make the tracking of the amplifier faster.Generally, the gain of the amplifier is normally expressed as A v= G m × R 0 where G m is the transconductance (e.g., the ratio of the current change at an output terminal to the voltage change at an input terminal of a device) of the input device, and R 0 is the load impedance as seen by the input device (e.g., if an electrical circuit has a uniquely defined output terminal, the circuit connected to the output terminal is the load; generally, the impedance is a measure of the resistance a circuit opposes a current when a voltage is applied). As used herein, the term "device" refers to an active electrical component of an electrical circuit including transistors and diodes (generally, the term is typically used for "active" components such as transistors rather than for "passive" components such as resistors). As R 0 is increased, the ability of the amplifier to change its output over the entire output range is decreased, in other words, tracking it.To achieve higher gain, the transconductance of MPP 16 and MPN 18 may be decreased, for example, by reducing the current or aspect ratio (width to length ratio (W / L)) of MPP 16 and MPN 18. However, reducing the current of load devices MPP 16 and MPN 18 is not feasible because the current also supplies input devices MNP 12 and MNN 14. The aspect ratio of MPP 16 and MPN 18 may be reduced; however, decreasing the aspect ratio may increase the drain-source voltage (V DS) of load devices MPP 16 and MPN 18, causing input devices MNP 12 and MNN 14 to fail to saturate.Because the diode-connected loads MPP 16 and MPN 18 consume voltage margin, a portion of the bias currents of the input transistors MNP 12 and MNN 14 may be provided by the current sources MPIP 20 and MPIN 22. For example, if MPP 20 and MPIN 22 carry a majority of the drain current of MNP 12 and MNN 14, the current through MPP 16 and MPN 18 is proportionally reduced, potentially reducing the transconductance of MPP 16 and MPN 18. Thus, the differential gain may be larger than in the case without the current sources MPIP 20 and MCPIN 22.In addition, current sources MPP 20 and MPIN 22 may derive current from load devices MPP 16 and MPN 18, such that load devices MPP 16 and MPN 18 may be sized smaller without affecting saturation of input devices MNP 12 and MNN 14. The gates of current sources MPIP 20 and MPIN 22 may be driven to an appropriate bias voltage (VBIASP) to enable operation as current sources. (Biasing is a method of building predetermined voltages or currents at various points of a circuit to allow proper operating conditions; some devices may require a steady state (DC) current or voltage to operate properly even when processing analog (AC) current or voltage - the AC voltage signal applied to it is superimposed on the DC bias current or voltage.)The higher gain with current sources MPIP 20 and MPPIN 22 may result in a reduced tracking speed, which is reduced because current sources MPIP 20 and MPPIN 22 provide a smaller current for potential change at the output node when the input terminals see a larger voltage change. Accordingly, in various embodiments, current sources MPIP 20 and MPIP 22 may be coupled to a bias controller 28 that turns off and subsequently turns on current sources MPIP 20 and MPIP 22 during tracking. The current sources MPIP 20 and MPIN 22 connected in parallel with the load devices MPP 16 and MPN 18 may be turned on or off by controlling the voltage VBIASPwith the bias control circuit 28. In one embodiment, when amplifier 10 tracks, bias controller 28 may drive VBIASP close to V dd( supply voltage), thus turning MPIP 20 and MPIN 22 off and making available additional current to change the potential at the output node, thereby increasing the tracking speed. If amplifier 10 is not tracking, bias controller 28 may drive VBIASP to its normal value to allow MPIP 20 and MCPIN 22 to operate as current sources, resulting in a high gain for amplifier 10. It should be noted that a negative bias voltage (VBIASN) may be applied to another transistor MNB 26, which may also be connected to ground; load devices MPP 16 and MPN 18 may be connected to V dd.In various embodiments, bias controller 28 may be implemented in any suitable manner according to various design considerations. Note that as the gain of the amplifier 10 changes using the bias controller 28, the stability of the amplifier 10 may also change. The stability of amplifier 10 may be treated by appropriately controlling values of amplifier compensation capacitors and / or resistors.Referring to FIG. 2:FIG. 2, a simplified circuit diagram illustrating another embodiment of the amplifier 10 is shown. The input transistors MPP 12 and MPN 14 are p-type metal oxide semiconductor (PMOS) transistors, and the load devices MNP 16 and MNN 18 and the current sources MNIP 20 and MNIN 22 are n-type metal oxide semiconductor (NMOS) transistors. The bias controller 24 controls the supply bias voltage VBIASNto be near GND when the amplifier 10 tracks, thus turning off the current sources MNIP 20 and MNIN 22. If amplifier 10 is not tracking, bias controller 24 may control VBIASN to its normal value to allow MNIP 20 and MNIN 22 to operate as current sources, resulting in a high gain for amplifier 10.Referring to FIG. 3 : FIG. 3, a simplified circuit diagram illustrating example details of an embodiment of the amplifier 10. Embodiments of amplifier 10 may be used in precharge buffers of certain analog-to-digital converters (ADCs). In embodiments of amplifier 10 in the precharge buffer, the increased gain does not degrade offsets (e.g., due to random mismatches) or does not decrease the tracking speed of amplifier 10.According to various embodiments, the current sources MP 28, MP 30, MP 32 and MP 34 may be added in parallel to the diode loads MPP 16 and MPN 18. The parallel current sources MP 28, MP 30, MP 32 and MP 34 may maintain offsets due to mismatch of the diode-connected loads MPP 16 and MPN 18, for example, because input-related offsets remain the same as without the current sources MP 28, MP 30, MP 32 and MP 34. Also, current sources MP28, MP30, MP32, and MP34 may be sized so that they do not add input-related offsets by themselves. The added current sources may decrease the transconductance G m of the load devices MPP 16 and MPN 18 and thus increase the gain of the amplifier. However, the high gain is achieved at the expense of a reduced tracking speed because current available at the output is much smaller for charging discharge capacitors (not shown). Accordingly, the transistor MP 36 may be added to function as a switch. When the amplifier 10 tracks, the node FINEB may be at a lower voltage and subsequently all parallel current sources MP 28, MP 30, MP 32 and MP 34 are turned off and all current flows into the charging of the load capacitors. When the tracking is completed, the voltage at node FINEB may be increased so that node IB 10UP takes gate voltage V GS to keep all current sources MP 28, MP 30, MP 32 and MP 34 turned on.In some embodiments, the signal FINEB may not be generated separately; any suitable signal that may indicate whether the amplifier 10 is in the coarse settling mode or the fine settling mode may be used to control the switch MP 36. For example, when an input voltage is applied, the output of the amplifier takes some time to reach a value stable over time. During the tracking time (i.e., coarse transient mode), the output of the amplifier moves to the final voltage value at its maximum possible speed. During the ringing time (i.e., fine settling mode), the amplifier recovers from tracking and the output voltage stops moving within some predefined error range. The signal FINEB and the switch MP 36 may enable fast tracking during coarse injection (e.g., when the amplifier 10 is in tracking mode) and high gain during fine injection (e.g., when the amplifier 10 is not in tracking mode). It should be noted that current sources MP 28, MP 30, MP 32 and MP 34 may remain turned on for the duration of the application of the input voltage to the amplifier.When the amplifier 10 switches from the coarse mode to the fine mode, the current sources MP 28, MP 30, MP 32 and MP 34 are turned on, reducing V GS for the diode loads MPP 16 and MPN 18. It should be noted that decreasing V GS may also decrease G m of devices in the next stage of amplifier 10. However, the gain of the next stage remains unaffected because a smaller V GS reduces I d and increases R out. Thus, more current can be used in the next stage during coarse tuning, whereas less current can be used in the next stage during fine tuning.Referring to FIGS. 4 : 4, a simplified flow diagram is illustrated illustrating example operations 50 that may be associated with an embodiment of the amplifier 10. In 52, the current sources (e.g., MPIP 20 and MPIN 22) may be turned off by, for example, bias controller 28 driving VBIASP to V dd. In 54, voltage V IN may be measured across input nodes. In 56, if voltage V IN is not greater than a predetermined voltage threshold indicating tracking is completed, at 58, the current sources (e.g., MPIP 20 and MCP 22) may be turned on to achieve a higher gain for amplifier 10. For example, voltage VBIASPmay be decreased by bias controller 28 to turn on current sources (e.g., MPIP 20 and MPIN 22).On the other hand, if it is determined at 56 that the voltage V IN is greater than the predetermined voltage threshold, a further determination may be made as to whether the current sources at 60 (e.g., MPIP 20 and MCPIN 22) are turned on. If they are not turned on (e.g., as would be the case if the amplifier tracked after the input voltage has been applied), the operations may proceed to 54 where the output voltage is measured. On the other hand, if the current sources (e.g., MPIP 20 and MPIN 22) are turned on (e.g., as would be the case if the input voltage is turned off and the amplifier begins tracking down), the operations return to 52 where the current sources (e.g., MPIP 20 and MPIN 22) may be turned off, for example, by bias controller 28 reducing voltage VBIASPto V dd.Referring to FIG. 5:FIG. 5, a simplified flow diagram is illustrated illustrating example operations 70 that may be associated with an embodiment of the amplifier 10. At 72, the current sources (e.g., MPIP 20 and MPIN 22) may be turned off by, for example, bias controller 28 driving VBIASP to V dd. Then, the amplifier 10 can achieve a high tracking speed. At 74, the time from the start of the voltage change to the input node (e.g., MNP 12 and MNN 14) may be measured (e.g., using any suitable timer). At 76, a determination may be made as to whether the measured time is greater than a predetermined time threshold (e.g., corresponding to the end of the tracking mode). For example, if the tracking speed of amplifier 10 is known, the time required to complete tracking may be calculated and selected as the predetermined time threshold. If the measured time is greater than the predetermined time threshold, at 78, the current sources (e.g., MPIP 20 and MPIN 22) may be turned on by, for example, bias controller 28 increasing VBIASP. Thereupon, the amplifier 10 can attain a high gain. On the other hand, if the measured time is less than the predetermined time threshold, the operations may proceed to measure the time at 74.Referring to FIGS. 6 : 6, a simplified flow diagram illustrating example operations 90 that may be associated with an embodiment of the amplifier 10. In 92, the current sources (e.g., MPIP 20 and MPIN 22) may be turned off by, for example, bias controller 28 driving VBIASP to V dd. Then, the amplifier 10 can achieve a high tracking speed. At 94, the time from the start of the voltage change to the input node (e.g., MNP 12 and MNN 14) may be measured (e.g., using any suitable timer). At 96, the bias controller 28 may gradually increase the bias voltage VBIASP. At 98, a determination may be made as to whether the measured time is greater than a predetermined time threshold (e.g., corresponding to the end of the tracking mode). If so in 100, the bias controller 28 may apply a maximum bias voltage VBIASPto the current sources (e.g., MPIP 20 and MCPIN 22). On the other hand, if the measured time is not longer than the predetermined time threshold (e.g., amplifier 10 is in tracking mode), the operations may return to measuring time at 94.Referring to FIG. 7:FIG. 7, a simplified flow diagram illustrating example operations 110 that may be associated with an embodiment of the amplifier 10. At 112, a control signal (e.g., voltage FINEB) may monitor the input voltage or the time elapsed since the start of the input voltage change. At 114, a determination may be made as to whether the amplifier 10 is in tracking mode. If the amplifier 10 is in tracking mode at 116, the current sources (e.g., MP 28, MP 30, MP 32, and MP 34) may be turned off (e.g., by turning off the switch MP 36) to increase the tracking speed. On the other hand, if the amplifier 10 is not in tracking mode at 118, the current sources (e.g., MP 28, MP 30, MP 32, and MP 34) may be turned on (e.g., by turning on switch MP 36) to increase the gain.It should be noted that references in this specification to various features (e.g., elements, structures, modules, components, steps, operations, characteristics, etc.) included in "one embodiment", "one embodiment", "another embodiment", "some embodiments", "various embodiments", "other embodiments", "an alternative embodiment", and the like are intended to mean that all such features are included in one or more embodiments of the present disclosure, but may or may not necessarily be combined in the same embodiments.In the discussion of the above embodiments, circuit components such as capacitors, clocks, dividers, inductors, resistors, amplifiers, switches, digital cores, transistors, and / or other components may be readily replaced, interchanged, or otherwise modified to accommodate the specific requirements of the circuits. It should also be noted that the use of complementary electronic chips, hardware, software, etc., provides a equally viable option for implementing the teachings of the present disclosure.In one embodiment, any number of the electrical circuits of the FIGURES may be implemented on a circuit board of an associated electronic chip. The circuit board may be a general circuit board that may carry various components of the internal electronic system of the electronic chip and may further provide connectors for other peripheral devices. In particular, the circuit board may provide the electrical connections with which the other components of the system may electrically communicate. Any suitable processors (including digital signal processors, microprocessors, supporting chipsets, etc.), memory elements, etc., may be properly interconnected to the circuit board based on specific configuration requirements, processing requirements, computer designs, etc. Other components, such as external memory, additional sensors, controllers for audio / video display, and other peripheral chips, may be connected to the circuit board as plug-in cards via cables or integrated into the circuit board itself.In another embodiment, the electrical circuits of the FIGURES may be implemented as single modules (e.g., a chip with associated components and circuits configured to perform a particular application or function), or may be implemented as plug-in modules in application specific hardware or electronic chips. It should be noted that specific embodiments of the present disclosure may be readily included in a system on a chip (SOC) package, either in part or as a whole. An SOC is an IC that integrates components of a computer or other electronic system into a single chip. It may comprise digital, analog, mixed signal and often radio frequency functions: they all may be provided on a single chip substrate. Other embodiments may include a multi-chip module (MCM) having multiple separate ICs located in a single electronic package and configured to closely cooperate with each other in the electronic package. In various other embodiments, the functionalities described herein may be implemented in one or more silicon cores in application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) and other semiconductor chips. In various other embodiments, the functionalities described herein may be implemented in emulation form as software or firmware running on one or more configurable (e.g., programmable) elements arranged in a structure supporting these functions.It is also mandatory to note that all specifications, dimensions and relationships outlined herein (e.g., the number of components, logical operations, etc.) have been provided by way of example and teaching only. Such information may vary widely without departing from the spirit of the present disclosure or the scope of the appended claims. The patent specifications are only for a non-limiting example and should be construed as such. In the foregoing description, embodiments have been described with respect to specific component arrangements. Various modifications and changes may be made to such embodiments without departing from the scope of the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.It should be noted that the operations discussed above with respect to the FIGURES are applicable to any integrated circuits involving signal processing, particularly those that rely on signals to execute specialized software programs or algorithms, some of which may be associated with processing digitized real-time data. Certain embodiments may relate to automotive applications, such as battery power sensors and associated accessories. Certain other embodiments may relate to multi-DSP signal processing, floating point processing, signal / control processing, fixed function processing, microcontroller applications, etc. In certain contexts, the features discussed herein may be applicable to automotive systems, medical systems, scientific gauges, wireless and wired communications, radio, industrial process control, audio and video devices, power sensing, gauges (which may be highly precise), and other systems based on digital processing.In addition, certain embodiments discussed above may be incorporated into digital signal processing technologies for medical imaging, patient monitoring, medical instrumentation, and home health care. These could include lung function monitors, accelerometers, heart rate monitors, pacemakers, etc. Other applications may involve automotive technologies for safety systems (e.g., stability control systems, driver assistance systems, braking systems, infotainment, and indoor applications of any type). Furthermore, powertrain systems (e.g., in hybrid and electric vehicles) may apply the functionalities described herein in high-precision data converter products in battery monitoring, control systems, protocol controllers, maintenance activities, etc.In still other example scenarios, the teachings of the present disclosure may be applicable in industrial markets, including process control systems that help promote productivity, energy efficiency, and reliability. In private customer applications, the teachings of the electrical circuitry discussed above may be used for image processing, autofocus, and image stabilization (e.g., for digital still cameras, camcorders, etc.). Other private customer applications may include audio and video processors for home kinematics systems, DVD recorders, and high definition televisions. Still other private customer applications may include sophisticated touch screen controls (e.g., for some type of portable media chip). Thus, such technologies may readily be part of smart phones, tablets, security systems, personal computers, gaming technology, virtual reality, simulation training, etc.It should be noted that with the numerous examples provided herein, the interaction may be described in terms of two, three, four, or more electrical components. However, this is done for clarity and as an example only. It will be appreciated that the system may be brought together in any suitable manner. In addition to similar design alternatives, any of the illustrated components, modules, and elements of the FIGURES may be combined in various possible configurations, all of which are clearly within the broad scope of this specification. In certain cases, it may be easier to describe one or more of the functionalities of a given set of flows by only referencing a limited number of electrical elements. It should be appreciated that the electrical circuits of the FIGURES and their teachings are readily scalable and can accommodate a large number of components as well as more complex / sophisticated arrangements and configurations. Accordingly, the examples provided should not limit the scope or block the broad teachings of the electrical circuits because they are potentially applied to numerous other architectures.Numerous other changes, substitutions, variants, alterations, and modifications may be ascertained to one skilled in the art, and it is intended that the present disclosure encompass all such changes, substitutions, variants, alterations, and modifications as they fall within the scope of the appended claims.OTHER NOTES, EXAMPLES AND IMPLEMENTATIONSIt should be noted that all optional features of the apparatus described above may also be implemented in terms of the method or process described herein, and details in the examples may be used anywhere in one or more embodiments. In a first example, a system is provided (which may include any suitable circuits, dividers, capacitors, resistors, inductors, ADCs, DFFs, logic gates, software, hardware, interconnects, etc.) that may be part of any type of electronic device (e.g., a computer) that may further include a circuit board interconnected with multiple electronic components. The system includes a high gain, high tracking speed amplifier including a pair of input transistors to which an input voltage is applied, a pair of diode connected loads coupled to the input transistors, at least one pair of current sources coupled to the diode connected loads, and a bias controller.The amplifier includes means for turning off the current sources with the bias control when the amplifier is tracking; and means for turning on the current sources with the bias control when the amplifier is not tracking; means for gradually increasing the bias voltage across the current sources with the bias control when the amplifier is tracking to gradually turn on the current sources; means for applying the input voltage to the input transistors; means for measuring the time starting from the application of the input voltage; and means for turning on the current sources with the bias control when the measured time exceeds a predetermined time threshold, for example, corresponding to an end of the tracking of the amplifier. The amplifier may further include means for measuring the output voltage of the amplifier; and means for turning on the current sources with the bias controller when the measured voltage exceeds a predetermined voltage threshold.The means for in these examples (above) may include (but are not limited to): using any suitable component discussed herein, along with any suitable software, circuitry, hub, computer code, logic, algorithm, hardware, controller, interface, link, bus, communication path, etc. In a second example, the system includes memory that further includes machine readable instructions that, when executed, cause the system to perform any of the activities discussed above.

Claims

A high gain, high tracking speed amplifier (10) comprising: a pair of input transistors (MNP 12, MNN 14) to which input voltages (IN+ and IN-) are applied; a pair of diode connected loads (MPP 16, MPN 18) connected to the input transistors (MNP 12, MNN 14); at least one pair of current sources (MPIP 20, MPIN 22) connected to the diode connected loads (MPP 16, MPN 18); and a bias controller (28) configured to turn off the at least one pair of current sources (MPIP 20, MCPIN 22) to enable a high tracking speed for the amplifier (10), wherein the bias controller (28) turns off the current sources (MPIP 20, MCPIN 22) during a coarse transient mode of the amplifier (10) when the amplifier (10) is tracking and turns on the at least one pair of current sources (MPIP 20, MCPIN 22) to enable a high gain for the amplifier (10), and wherein the bias controller (28) turns on at least one pair of current sources (MPIP 20, MCPIN 22) at the end of tracking and keeps the current sources (MPIP 20, MCPIN 22) turned on when the amplifier (10) is not tracking.Amplifier (10) according to claim 1, wherein the current sources comprise transistors, wherein the bias controller (28) controls a bias voltage (VBIASP) to the current sources (MPIP 20, MCPIN 22), wherein the bias voltage (VBIASP) is driven to the supply voltage (V dd) to turn off the current sources (MPIP 20, MCPIN 22).The amplifier (10) of any preceding claim, wherein the bias controller (28) gradually increases the bias voltage (VBIASP) as the amplifier (10) tracks to gradually turn on the current sources (MPIP 20, MPIN 22).The amplifier (10) of any preceding claim, wherein the bias controller (28) includes a transistor switch coupled to the current sources (MPIP 20, MPIN 22), the current sources (MPIP 20, MPIN 22) being turned on when the transistor switch is turned on, the current sources (MPIP 20, MPIN 22) being turned off when the transistor switch is turned off.The amplifier (10) of any preceding claim, wherein the bias controller (28) turns off the current sources (MPIP 20, MPIN 22) when a time measured from a start of application of the input voltage to the input transistors is below a predetermined time threshold, and the bias controller (28) turns on the current sources (MPIP 20, MPIN 22) when the measured time is above the predetermined time threshold.The amplifier (10) of claim 5, wherein the predetermined time threshold corresponds to an end of tracking of the amplifier (10).The amplifier (10) of any preceding claim, wherein the bias controller (28) turns off the current sources (MPIP 20, MPIN 22) when the output voltage of the amplifier (10) is below a predetermined voltage threshold, and the bias controller (28) turns on the current sources (MPIP 20, MPIN 22) when the output voltage of the amplifier is above a predetermined voltage threshold.The amplifier (10) of any preceding claim, wherein the amplifier (10) is used in a precharge buffer of an analog-to-digital converter (ADC).An amplifier (10) having a high gain and a high tracking speed, comprising: a pair of input transistors (MPP 12, MPN 14) to which input voltages (IN+ and IN-) are applied; a pair of diode-connected loads (MNP 16, MNN 18) connected to the input transistors (MPP 12, MPN 14); at least one pair of current sources (MNIP 20, MNIN 22) connected to the diode-connected loads (MNP 16, MNN 18); and a bias controller (24) configured to turn off the at least one pair of current sources (MNIP 20, MNIN 22) to enable a high tracking speed for the amplifier (10), wherein the bias controller (24) drives the current sources (MNIP 20, The method of driving the amplifier (10) into a OFF state during a coarse transient mode of the amplifier (10) when the amplifier (10) is tracking and into a ON state the at least one pair of current sources (MNIP 20, MPIP 22) to allow a high gain for the amplifier (10), and wherein the bias controller (24) turns on at least one pair of current sources (MPIP 20, MPIN 22) at the end of tracking and keeps the current sources (MNIP 20, MNIN 22) turned on when the amplifier (10) is not tracking, and wherein the input transistors (MPP 12, MPN 14) comprise p-type metal oxide semiconductor (PMOS) transistors and the diode-connected loads and the current sources comprise n-type metal oxide semiconductor (NMOS) transistors.A method of enabling a high gain, high tracking speed amplifier (10) comprising a pair of input transistors (MNP 12, MNN 14) to which input voltages (IN+ and IN-) are applied, a pair of diode connected loads connected to the input transistors (MNP 12, MNN 14), at least one pair of current sources (MPIP 20, MCPIN 22) connected to the diode connected loads, and a bias controller (28), the method comprising: turning off the current sources with the bias controller (28) during a coarse settling mode of the amplifier (10) when the amplifier (10) is tracking; and turning on the current sources with the bias controller (28) when the amplifier (10) is not tracking.Method according to claim 10, wherein the current sources comprise transistors, wherein the bias controller (28) controls a bias voltage (VBIASP) to the current sources (MPIP 20, MCPIN 22), wherein the bias voltage (VBIASP) is driven to the supply voltage (V dd) in order to switch off the current sources (MPIP 20, MCPIN 22).The method of claim 11, further comprising gradually increasing the bias voltage (VBIASP) with the bias controller (28) as the amplifier (10) tracks to gradually turn on the current sources (MPIP 20, MPIN 22).The method of any of claims 10 to 12, wherein the bias controller (28) includes a transistor switch coupled to the current sources (MPIP 20, MCPIN 22), the current sources being turned on when the transistor switch is turned on, the current sources (MPIP 20, MCPIN 22) being turned off when the transistor switch is turned off.The method of any of claims 10 to 13, further comprising: turning off the current sources (MPIP 20, MPIN 22) with the bias controller (28); applying the input voltage (IN+ and IN-) to the input transistors (MNP 12, MNN 14); measuring time beginning with the application of the input voltage (IN+ and IN-); and turning on the current sources (MPIP 20, MPIN 22) with the bias controller (28) if the measured time exceeds a predetermined time threshold.The method of claim 14, wherein the predetermined time threshold corresponds to an end of tracking of the amplifier (10).The method of any of claims 10 to 15, further comprising: turning off the current sources (MPIP 20, MPIN 22) with the bias controller (28); applying the input voltage (IN+ and IN-) to the input transistors (MNP 12, MNN 14); measuring the output voltage of the amplifier (10); and turning on the current sources (MPIP 20, MPIN 22) with the bias controller (28) when the measured voltage exceeds a predetermined voltage threshold.A method of enabling a high gain, high tracking speed amplifier (10) comprising a pair of input transistors (MPP 12, MPN 14) to which input voltages (IN+ and IN-) are applied, a pair of diode connected loads coupled to the input transistors (MPP 12, MPN 14), at least one pair of current sources (MNIP 20, MNIN 22) coupled to the diode connected loads, and a bias controller (24), the method comprising: turning off the current sources (MNIP 20, MNIN 22) with the bias controller (24) during a coarse settling mode of the amplifier (10) as the amplifier (10) tracks; and turning on the current sources (MNIP 20, MNIN 22) with the bias controller (24) when the amplifier (10) is not tracking, and wherein the input transistors (MPP 12, MPN 14) COMPRISE PMOS transistors and the diode-connected loads and the current sources comprise NMOS transistors.

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