A conversion circuit using common base as front stage V / I and back stage as I / V

Abstract

A conversion circuit using a common base as the front stage V / I and the back stage as I / V. (1) Because the differential input stage in the analog amplifier is composed of a common emitter circuit, it hinders the development of the input signal to high frequency and high speed. For this reason, the present invention designs an input stage circuit composed of a common base circuit. We know that the f T Compared with the common-emission method, f T The bandwidth is increased by β times of the tube itself. By utilizing this advantage of the common base circuit, a wide-band, high-speed circuit can be designed. (2) The final stage is used as an I / V conversion circuit. In analog amplifiers, in order to reduce the crossover distortion caused by the large current push-pull of the end tube, the static current of the end-stage push-pull tube is usually designed to be large, which is called Class A. The design method of Class B is to only give the end tube a very small static current and allow crossover distortion to exist, in order to save costs, but it will significantly affect the sound quality. For this reason, this circuit designs a super Class A circuit. It is composed of a common base circuit and only requires the static current of Class B to eliminate crossover distortion. It reduces costs and saves energy. It belongs to analog electronics and is used in high-speed circuits or audio fields.

Description

Technical Field

[0001] The present invention relates to (1) a V / I converter having a common base input stage; (2) a power amplifier circuit used as an I / V converter in a subsequent stage or an input / output circuit requiring high-speed transmission, and more particularly to (1) a super Class A circuit in which a common base input stage replaces a common emitter differential input stage; and (2) a subsequent stage is used to eliminate crossover distortion.

[0002] It is an analog electronic technology and is mainly used in high-speed circuits or audio fields. Background Art

[0003] (1) At present, in the digital age, circuits are developing towards high frequency and high speed. The analog circuits connected to digital circuits in the past can no longer adapt to the development of the current era. This is because the differential input amplifier circuits in analog amplifier circuits are all composed of common emitter circuits, which hinders the development of input signals towards high frequency and high speed. We know that the f T Compared with the common-emission method, f T The bandwidth is increased by β times of the tube itself. By utilizing this advantage of the common base circuit, a wide-band and high-speed circuit can be designed. However, the input resistance of the common-emitter circuit is about β times higher than that of the common-base circuit. This is why the differential circuit is designed in a common-emitter manner. In other words, the purpose can be achieved by simply increasing the input resistance of the common-base circuit. For this reason, the present invention adds a constant current source circuit to the common base circuit, thereby achieving the purpose of replacing the traditional differential input stage with the common-base V / I circuit.

[0004] (2) In analog amplifiers, in order to reduce the crossover distortion caused by one tube being turned on and the other tube being turned off when the high current push-pull operation of the final tube is carried out, the usual practice is to design the quiescent current of the final push-pull tube to the required maximum dynamic current value, so as to ensure that one tube is turned on and the other tube is not turned off in the entire dynamic current working area. This design is called Class A. The smaller the load resistance, the larger the current is designed. In addition to increasing the cost, it also wastes energy. The practice of designing it as Class B is to only give the final tube a very small quiescent current and allow the crossover distortion to exist, so as to save cost, but it will obviously affect the sound quality. For this reason, this circuit designs a super Class A circuit, which is composed of a common base circuit. Only the quiescent current of Class B is needed to eliminate the crossover distortion. No matter how the load impedance RL changes, it can ensure that there is no crossover distortion, which reduces cost and saves energy. This is the advantage of using I / V in the final stage. Summary of the Invention

[0005] To overcome the bandwidth problem currently caused by the common-emitter differential circuit design, the present invention (1) designs a common-base current negative feedback conversion circuit with a common-base circuit, a common-base current, and a large-loop negative feedback circuit. This circuit solves the narrow operating bandwidth problem of the common-emitter differential circuit and achieves the purpose of increasing the input stage bandwidth. In addition, the present invention (2) uses the common-base circuit's I / V in the back stage to convert the static high current of the class A final stage tube into the static low current of the class B final stage tube, while achieving performance equivalent to that of the class A circuit, thereby solving the problem of crossover distortion caused by the static low current of the class B final stage tube.

[0006] The V / I converter of the present invention (1) has a specific circuit design scheme as follows: In order to increase the input resistance, the common base tubes Q4 and Q5 at the in-phase input end are designed to work in a constant current state regardless of whether they are dynamic or static. To achieve this purpose, a constant current source circuit must be designed. This constant current device can use a constant current tube, but the price of a constant current tube is relatively high. Therefore, the author uses the U1LM317LZ (this tube is a TO-92 package) with low price and constant current performance that is basically not affected by ambient temperature changes and has higher stability than the constant current tube, and connects it to a constant current source circuit. In source form, Q1, Q3, Q2, and Q6 are used to isolate R2, R5, R4, and R8 as mirror-proportional current sources, so that the current entering IR2 and IR4 (R2=R4) is converted into voltage to further control VR5 and VR8 (R5=R8). Then VR5 and VR8 convert the voltage into current to provide the static current of the common-base tubes Q4 and Q5. In dynamic mode, if the input signal voltage is positive, the signal current will pass through R7→Q5 into Q6 and reach R8, but VR8 is locked by VR4, so the signal The signal current cannot enter R8, that is, the emitter of Q5 at this time only accepts the input signal voltage, not the input signal current, that is, the input current at point B is basically zero, and the circuit on the upper side of point B still maintains the original static current unchanged; similarly, when the negative half-cycle signal voltage comes, the signal current will be provided by R6→Q4→Q3→R5, but VR5 is locked by VR2, so the signal current cannot be obtained from R5, that is, the emitter of Q4 at this time only accepts the input signal voltage, not the input signal current, that is, the input current at point B during the negative half-cycle signal is basically zero. The original static current is zero, while the circuit below point B still maintains the original static current basically unchanged. From the above analysis, it can be seen that the input resistance of this common base input connection is very large regardless of the input positive or negative signal, and point B = point C regardless of the positive or negative input signal voltage. In the circuit, when R10 = R11 = R6 = R7, IQ8 = IQ9 = IQ4 = IQ5, so that the common base input circuit is converted from voltage input to enable Q8 and Q9 to have the ability to output current, achieving V / I conversion, making the common base circuit as the input stage voltage and improving the availability of bandwidth. The circuit connection method is, +Vcc→R2→Q1 emitter and collector (collector connected to Q1 and Q3 base)→U1's IN terminal, U1's output terminal→R3→Q2 collector (collector connected to U1's ADJ connected to Q2 and Q6 base), emitter→R4→-Vcc, +Vcc→R5→Q3's emitter and collector→Q4 collector (collector connected to Q4 and Q8 base), emitter→R6→point B→R7→Q5 emitter and collector (collector connected to Q5 and Q9 base)→Q6 collector and emitter→R8→-Vcc, +Vcc→R9→Q7 emitter and collector (collector connected to Q7 and Q11 base)→Q8 collector and emitter→R10→point C→R11→Q9 emitter and collector→Q10 collector (collector connected to Q10 and Q14 base), emitter→R12→-Vcc.

[0007] The I / V converter of the present invention (2) has a specific circuit design as follows: In a power amplifier, a constant voltage circuit for the final tube is generally designed to stabilize the static current of the final tube, but the disadvantage is that crossover distortion will occur during dynamic operation. The principle is that Q21 provides a positive dynamic current to RL from R24. The greater the current on RL, the higher the dynamic voltage on R24, which causes the voltage on R25 to decrease. Assuming that the static current of R24 and R25 is 5mA, when the forward current flowing through R24 exceeds 10mA, the voltage on R25 decreases. The current is zero, the emitter current of Q22 is zero, so Q22 is cut off, which is the positive half-cycle crossover distortion; in the negative half-cycle, when the current on RL flows through R25 and exceeds 10mA, the current of R24 is zero, the emitter current of Q21 is zero, so Q21 is cut off, which is the negative half-cycle crossover distortion. In order to solve the crossover distortion problem, the following circuit is designed. R22 and Q19 are added in the positive half-cycle, and R23 and Q20 are added in the negative half-cycle. Its working principle is that when the positive half-cycle signal current enters RL through R24, let V BE21 ≈V BE19 , when R22=R19, ΔVR24≈ΔVR22=ΔVR19, that is, ΔIR22=ΔIR19, completing the positive dynamic process of I / V conversion of Q19; similarly, when the negative half-cycle signal current enters R25 through RL, let V BE22 ≈V BE20 When R23 = R17, ΔVR25 ≈ ΔVR23 = ΔVR17, meaning ΔIR23 = ΔIR17, completing the negative dynamics of Q20's I / V conversion. Because the I / V conversion utilizes a common-base circuit, it boasts fast conversion speed and wide bandwidth. The circuit connections are: Q21 base → R22 → Q19 emitter and collector → the top of R19, with Q19 base connected to terminal Vo; Q22 base → R23 → Q20 emitter and collector → the bottom of R17, with Q20 base connected to terminal Vo; +Vcc → Q21 collector and emitter → R24 → terminal Vo → R25 → Q22 emitter and collector → -Vcc.

[0008] The beneficial effects of the (1) V / I and (2) I / V converters of the present invention are as follows: since the circuit uses a common base circuit with in-phase and inverting inputs from the input end, the circuit has a high transmission rate, a wide frequency band and a high signal-to-noise ratio. The large loop negative feedback network of the circuit is connected to the inverting input end C, forming a current negative feedback, so that the loop negative feedback speed of the circuit is improved, thereby the feedback signal at point C can quickly keep up with the input signal at point B within a wider frequency band (when the Vi signal is input, the waveforms at points B and C are highly overlapped on the oscilloscope display); actual listening shows that the (1) V / I and (2) I / V converters of the present invention, after forming the overall circuit: the high pitch is clear, the sibilance is clearly audible, and the sound quality is soft and pleasant, while the differential circuit and class B power amplifier composed of the common emitter circuit in the prior art have a hard and astringent sound quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The present invention adopts (1) common base as the front stage V / I and the back stage as (2) I / V conversion circuit diagram.

[0010] Specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION

[0011] This circuit uses Figure 1 The B terminal is the non-inverting input terminal, and its circuit connection method is: +Vcc→R2→Q1 emitter, collector (collector connected to Q1, Q3 base)→U1 IN terminal U1 output terminal→R3→Q2 collector (collector connected to U1 ADJ connected to Q2, Q6 base), emitter→R4→-Vcc, +Vcc→R5→Q3 emitter, collector→Q4 collector (collector connected to Q4, Q8 base), emitter→R6→B point→R7→Q5 emitter, collector ( Collector connected to Q5, Q9 base) → Q6 collector, emitter → R8 → -Vcc, +Vcc → R9 → Q7 emitter, collector (collector connected to Q7, Q11 base) → Q8 collector, emitter → R10 → point C → R11 → Q9 emitter, collector → Q10 collector (collector connected to Q10, Q14 base), emitter → R12 → -Vcc, +Vcc → R15 → Q11 emitter, collector → Q12 collector (one end of R17 connected to Q12 The other end of the collector is connected to Q12, the base is connected to R18, the other end of R18 is connected to Q13 base, Q13 base is connected to one end of R19, the other end of R19 is connected to Q13 collector), emitter → Q13 emitter, collector → Q14 collector, emitter → R16 → -Vcc, +Vcc → Q15 collector (base connected to R17), emitter → Q16 collector (collector connected to Q16, Q21 base), emitter → R20 → Vo → R21 → Q17 emitter, collector (collector Base connected to Q17, Q22 base) → Q18 emitter (base connected to R19), collector → -Vcc, Q21 base → R22 → Q19 emitter and collector → upper end of R19, Q19 base connected to Vo terminal, Q22 base → R23 → Q20 emitter and collector → lower end of R17, Q20 base connected to Vo terminal, +Vcc → Q21 collector and emitter → R24 → Vo terminal → R25 → Q22 emitter and collector → -Vcc, Vo terminal → RL → ground.

Claims

1. A conversion circuit using a common base as the front stage V / I and the back stage as the I / V, characterized in that: (1) One end of the positive power supply +Vcc is electrically connected to one end of the resistor R2, the other end of R2 is electrically connected to the emitter of the switching tube Q1, the base of the switching tube Q1 is electrically connected to the base of the switching tube Q3, the base of the switching tube Q1 is electrically connected to the collector of the switching tube Q1, the collector of the switching tube Q1 is electrically connected to the IN end of the three-terminal voltage regulator U1, the output end of the three-terminal voltage regulator U1 is electrically connected to one end of the resistor R3, the other end of the resistor R3 is electrically connected to the collector of the switching tube Q2, the collector of the switching tube Q2 is electrically connected to the ADJ end of the three-terminal voltage regulator U1, the base of the switching tube Q2 is electrically connected to the base of the switching tube Q6, the base of the switching tube Q2 is electrically connected to the collector of the switching tube Q2, the emitter of the switching tube Q2 is electrically connected to one end of the resistor R4, the other end of the resistor R4 is electrically connected to one end of the negative power supply -Vcc, the positive power supply +V One end of cc is electrically connected to one end of resistor R5, the other end of resistor R5 is electrically connected to the emitter of switching tube Q3, the collector of switching tube Q3 is electrically connected to the collector of switching tube Q4, the base of switching tube Q4 is electrically connected to the base of switching tube Q8, the base of switching tube Q4 is electrically connected to the collector of switching tube Q4, the emitter of switching tube Q4 is electrically connected to one end of resistor R6, the other end of resistor R6 is electrically connected to point B, the input end Vi is electrically connected to point B, the input end Vi is electrically connected to one end of resistor R1, the other end of resistor R1 is electrically connected to ground, point B is electrically connected to one end of resistor R7, the other end of resistor R7 is electrically connected to the emitter of switching tube Q5, the base of switching tube Q5 is electrically connected to the base of switching tube Q9, the base of switching tube Q5 is electrically connected to the collector of switching tube Q5, and the collector of switching tube Q5 is electrically connected to switch The collector of the switching tube Q6, the emitter of the switching tube Q6 is electrically connected to one end of the resistor R8, the other end of the resistor R8 is electrically connected to one end of the negative power supply -Vcc, one end of the positive power supply +Vcc is electrically connected to one end of the resistor R9, the other end of the resistor R9 is electrically connected to the emitter of the switching tube Q7, the base of the switching tube Q7 is electrically connected to the base of the switching tube Q11, the base of the switching tube Q7 is electrically connected to the collector of the switching tube Q7, the collector of the switching tube Q7 is electrically connected to the collector of the switching tube Q8, the emitter of the switching tube Q8 is electrically connected to one end of the resistor R10, the other end of the resistor R10 is electrically connected to point C, point C is electrically connected to one end of the resistor R13, the other end of the resistor R13 is electrically connected to ground, point C is electrically connected to one end of the resistor R11, and the other end of the resistor R11 is electrically connected to the emitter of the switching tube Q9. The electrode is electrically connected to the collector of the switching tube Q10, the base of the switching tube Q10 is electrically connected to the base of the switching tube Q14, the base of the switching tube Q10 is electrically connected to the collector of the switching tube Q10, the emitter of the switching tube Q10 is electrically connected to one end of the resistor R12, the other end of the resistor R12 is electrically connected to one end of the negative power supply -Vcc, one end of the positive power supply +Vcc is electrically connected to one end of the resistor R15, the other end of the resistor R15 is electrically connected to the emitter of the switching tube Q11, the collector of the switching tube Q11 is electrically connected to the collector of the switching tube Q12, the emitter of the switching tube Q12 is electrically connected to the emitter of the switching tube Q13, the collector of the switching tube Q13 is electrically connected to the collector of the switching tube Q14, the emitter of the switching tube Q14 is electrically connected to one end of the resistor R16, the other end of the resistor R16 is electrically connected to one end of the negative power supply -Vcc,The collector of the switching tube Q12 is electrically connected to one end of the resistor R17, the other end of the resistor R17 is electrically connected to the base of the switching tube Q12, the base of the switching tube Q12 is electrically connected to one end of the resistor R18, the other end of the resistor R18 is electrically connected to the base of the switching tube Q13, the base of the switching tube Q13 is electrically connected to one end of the resistor R19, the other end of the resistor R19 is electrically connected to the collector of the switching tube Q13, (2) One end of the positive power supply +Vcc is electrically connected to the collector of the switch tube Q15, the base of the switch tube Q15 is electrically connected to the collector of the switch tube Q12, the emitter of the switch tube Q15 is electrically connected to the collector of the switch tube Q16, the base of the switch tube Q16 is electrically connected to the base of the switch tube Q21, the base of the switch tube Q16 is electrically connected to the collector of the switch tube Q16, the emitter of the switch tube Q16 is electrically connected to one end of the resistor R20, the other end of the resistor R20 is electrically connected to the output terminal Vo, and the output terminal Vo is electrically connected to the resistor One end of resistor R21, the other end of resistor R21 is electrically connected to the emitter of switching tube Q17, the base of switching tube Q17 is electrically connected to the base of switching tube Q22, the base of switching tube Q17 is electrically connected to the collector of switching tube Q17, the collector of switching tube Q17 is electrically connected to the emitter of switching tube Q18, the base of switching tube Q18 is electrically connected to the collector of switching tube Q13, the collector of switching tube Q18 is electrically connected to one end of negative power supply -Vcc, the base of switching tube Q21 is electrically connected to one end of resistor R22, resistor R22 The other end is electrically connected to the emitter of the switch tube Q19, the base of the switch tube Q19 is electrically connected to the output terminal Vo, the collector of the switch tube Q19 is electrically connected to the base of the switch tube Q13, the base of the switch tube Q12 is electrically connected to the collector of the switch tube Q20, the base of the switch tube Q20 is electrically connected to the output terminal Vo, the emitter of the switch tube Q20 is electrically connected to one end of the resistor R23, the other end of the resistor R23 is electrically connected to the base of the switch tube Q22, one end of the positive power supply +Vcc is electrically connected to the collector of the switch tube Q21, and the switch tube Q The emitter of 21 is electrically connected to one end of the resistor R24, the other end of the resistor R24 ​​is electrically connected to the output end Vo, the output end Vo is electrically connected to one end of the resistor R25, the other end of the resistor R25 is electrically connected to the emitter of the switch tube Q22, the collector of the switch tube Q22 is electrically connected to one end of the negative power supply -Vcc, the output end Vo is electrically connected to one end of the output load RL, the other end of the output load RL is electrically connected to ground, the output end Vo is electrically connected to one end of the resistor R14, and the other end of the resistor R14 is electrically connected to the C end.

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