Improved exponential rising waveform generation circuit for neuro-electrical stimulation

Abstract

The application discloses an improved exponential rising waveform generating circuit for nerve electric stimulation and belongs to the technical field of integrated circuits. The application is based on a CMOS process and is composed of a constant current group, a time-dependent current group and an amplification current group. Through switch control, the exponential rising current based on the Taylor approximation principle is output. By adjusting the current multiple of the internal current mirror, the size of the capacitor and the parameters of each current reference, the output range and duration of the exponential rising current can be expanded. The amplification current group can expand the output range by several times, which is conducive to quickly causing nerve activity. The circuit has the advantages of simple structure, small area, fast response speed, wide output range, small temperature influence, low power consumption, continuous exponential rising current, few control terminals, easy chip integration control and wide application in the biological medical field such as nerve stimulators.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to an improved exponentially rising waveform generation circuit for nerve electrical stimulation. Background Technology

[0002] Traditional medical devices face the challenge of lacking precise and non-invasive methods for treating affected areas. In the biomedical field, neurostimulators can target biological tissues with electrical charges, inducing neural activity at corresponding locations and thus affecting the organism. Currently, biomedical technology is widely used in areas such as epilepsy detection and suppression, artificial retinal prostheses, and cochlear implants.

[0003] Currently, there is a significant need for biomimetic waveform stimulation (similar to the stimulation of neural activity in living organisms) to stimulate the whole-brain network required for dynamic memory processing. Biomimetic waveform stimulation consists of two parts: an exponentially rising waveform and an exponentially decaying waveform. However, current circuits using subthreshold and pure current schemes to generate exponentially rising waveforms suffer from higher power consumption, smaller output range, slower response speed, and greater susceptibility to temperature fluctuations, making them unsuitable for many biomedical fields. Summary of the Invention

[0004] The purpose of this invention is to provide an improved exponentially rising waveform generation circuit for nerve electrical stimulation, which solves the problems of high power consumption, small output range, slow response speed and susceptibility to temperature in current exponentially rising current generation circuits. It has the characteristics of large output range, low temperature susceptibility, fast response speed and low power consumption, and can be well applied in the biomedical field.

[0005] To achieve the above objectives, the present invention provides an improved exponentially rising waveform generation circuit for nerve electrical stimulation, comprising a constant current group, a time-dependent current group, and an amplified current group. The constant current group consists of transistors five and six, used to provide the constant term in the Taylor approximation expression for the exponentially rising current; the drain and gate of transistor six are shorted and connected to the constant current reference; the gates of transistors five and six are connected, and their sources are both grounded; the drain current of transistor five and the drain current of transistor two constitute the exponentially rising current. A constant current reference is connected to the power supply voltage. The time-dependent current group consists of transistor 1, transistor 2, a capacitor, switch 1, switch 2, transistor 3, and transistor 4. It provides the rising term in the Taylor approximation expression for the exponentially rising current. Transistor 1 has its drain and gate shorted, one end connected to the time-dependent current reference and switch 1, and its source connected to ground. The drain currents of transistor 2 and 5 together form the exponentially rising current. The gate of transistor 1 is connected to switch 2 and capacitor, and the source is connected to ground. One end of capacitor is connected to one end of switch 1, switch 2 and transistor 2, and the other end is connected to ground. One end of switch 1 is connected to transistor 1, and the other end is connected to switch 2, transistor 2 and capacitor. One end of switch 2 is connected to switch 1, transistor 2 and capacitor, and the other end is connected to one end of transistor 4. The drain and gate of transistor 3 are shorted, one end is connected to the charging current reference and transistor 4, and the source is connected to the power supply voltage. The gate of transistor 4 is connected to one end of transistor 3, the source is connected to the power supply voltage, and the drain is connected to switch 2. The current amplification group consists of transistors seven and eight, used to convert the exponentially rising current generated by the constant current group and the time-dependent current group. This is amplified to produce the final exponentially increasing current. Transistor 7 has its drain and gate shorted, with one end connected to the drains of transistors 2 and 5, as well as transistor 8. Its source is connected to the power supply voltage. Transistor 8 has one end connected to transistor 7, and its drain current is the exponentially increasing current of the final output. The source is connected to the power supply voltage; The constant current reference provides a current reference for the constant current group; the time-dependent current reference provides a current reference for the time-dependent current group; and the charging current reference provides a current reference for the time-dependent current group.

[0006] Preferably, transistors 1, 2, 5, and 6 are all NMOS transistors, while transistors 3, 4, 7, and 8 are all PMOS transistors, with the final output current... For pulling current.

[0007] Preferably, transistors 1, 2, 3, 4, 5, 6, 7 and 8 all operate in the saturation region.

[0008] Preferably, the current value of the charging current reference is several orders of magnitude smaller than that of the constant current reference and the time-dependent current reference, so as to slowly inject charge into the capacitor through the charging current reference, thereby increasing the gate voltage of transistor two and increasing the final output current. The exponential increase in current pulse width.

[0009] Preferably, the time-dependent current reference and the constant current reference are not equal, with the constant current reference being larger than the time-dependent current reference, in order to increase the final output current. The exponential increase in current pulse width.

[0010] Preferably, both switch one and switch two are transistor switches, which are turned on and off according to the gate voltage, so as to facilitate chip integration and digital control.

[0011] Preferably, the size and physical parameters of the transistors constituting the current mirror in the time-dependent current group and the constant current group can be set according to actual needs.

[0012] Preferably, the amplified current group controls the final output current through the ratio between transistor seven and transistor eight. The magnitude of the initial output current allows for an exponentially increasing current output range that can be extended several times over.

[0013] Preferably, the method for generating this circuit includes the following steps: S1. In the initial state, all switches are in the open state, and the current output is... Determined by the constant current group, the output is a constant current at this time; S2. Close switch one, current output. The current is determined by the constant current group, the time-dependent current reference, transistor one, and transistor two; at this time, it is a constant current. S3. Determine the required current output range based on the application, and control the final output current using the ratio between transistor seven and transistor eight. The magnitude of the initial output current, and the final output current at this time. As shown below, the input and output magnification of the current mirror in the time-dependent current group and the constant current group are both set to 1. and The reference currents output by the time-dependent current reference and the constant current reference, respectively: = ; ; Will and The equations are obtained by replacing them with the current-voltage equations of NMOS transistors two and five operating in the saturation region, where... These are characteristic parameters of a transistor. and These are the gate voltages of transistors five and two. The turn-on voltage of the transistor: ; ; S4. Disconnect switch one. Because the capacitor stores charge, the gate voltage of transistor two in the time-dependent current group remains unchanged, and the current supplied by the time-dependent current group remains unchanged. The final output current... Remain unchanged; S5. When switch two is closed, the charging current reference begins to affect the time-dependent current group. Charge is injected into the capacitor through the charging current reference, transistor three, and transistor four. The gate voltage of transistor two continuously increases with time. At this time, the output current of the time-dependent current group and the constant current group... Let be the exponentially increasing current that increases continuously with time, obtained through the Taylor approximation scheme, i.e., the exponentially rising current, where The reference current output is the charging current reference. Here is the capacitance value of the capacitor: ; Depending on the given current reference, the circuit... Greater than Both are constants, and since the physical parameters of transistor two and transistor five are exactly the same, and The difference is also a constant, and this constant is assumed to be... And by substituting the values ​​into the calculation, we get: ; This yields a current that increases exponentially with time, which is then amplified by a current amplifier and output at the output terminal. The final exponentially rising current waveform is obtained.

[0014] Therefore, the improved exponentially rising waveform generation circuit for nerve electrical stimulation using the above-described structure of the present invention has the following beneficial effects: (1) The present invention has a larger output range, which can meet the needs of the biomedical field for inducing neural activity. At the same time, due to the larger output range, the pulse width of the exponentially rising current waveform is extended, which can ensure that the nerve stimulator can work stably in more medical fields.

[0015] (2) The present invention has a faster response speed and lower power consumption compared to the exponentially rising current generation circuit based on the pure current scheme.

[0016] (3) The present invention exhibits less change in the exponentially rising current waveform under the influence of temperature, making it applicable to a wider range of biomedical applications. The waveform shift is only 25% between -40℃ and 80℃, while the exponentially rising waveform using the subthreshold scheme shifts by as much as 473% between 0℃ and 50℃.

[0017] (4) The circuit structure of the present invention is simple and has a small area. It can share capacitors with other circuits in the neurostimulator, saving area. At the same time, it has fewer control terminals, which is beneficial for control in the chip.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 This is a circuit diagram of an improved exponentially rising waveform generation circuit for nerve electrical stimulation according to the present invention.

[0020] Figure Labels 100 - Transistor 1; 101 - Transistor 2; 102 - Capacitor; 103 - Switch 1; 104 - Switch 2; 105 - Transistor 3; 106 - Transistor 4; 107 - Time-dependent current reference; 108 - Charging current reference; 109 - Time-dependent current group; 110 - Transistor 5; 111 - Transistor 6; 112 - Constant current reference; 113 - Constant current group; 114 - Transistor 7; 115 - Transistor 8; 116 - Amplification current group; 117 - Exponentially rising current ;118-Exponential Rising Current ;119 - Power supply voltage; 120 - Ground. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] Example like Figure 1 As shown, this invention provides an improved exponentially rising waveform generation circuit for nerve electrical stimulation. The circuit structure consists of three parts: transistors 110 (5) and 111 (6) form a constant current group 113, which is a constant term in a Taylor series approximation. The drain and gate of transistor 111 are shorted and connected to a constant current reference 112. The gates of transistors 110 and 111 are connected, and their sources are all grounded 120. The drain current of transistor 110 and the drain current of transistor 101 form an exponentially rising current. 117. The constant current reference 112 is connected to the power supply voltage 119.

[0024] Transistor 100, transistor 101, capacitor 102, switch 103, switch 104, transistor 105, and transistor 106 constitute time-dependent current group 109, which is the rising term of the Taylor series approximation. Transistor 100 has its drain and gate shorted, one end connected to the time-dependent current reference 107 and switch 103, and its source connected to ground 120. The drain current of transistor 101 and the drain current of transistor 110 constitute an exponentially rising current. 117. The gate of transistor 105 is connected to switch 103, switch 104, and capacitor 102, and the source is connected to ground 120. One end of capacitor 102 is connected to one end of switch 103, switch 104, and transistor 101, and the other end is connected to ground 120. One end of switch 103 is connected to transistor 100, and the other end is connected to switch 104, transistor 101, and capacitor 102. One end of switch 104 is connected to one end of switch 103, transistor 101, and capacitor 102, and the other end is connected to one end of transistor 106. Transistor 105 has its drain and gate shorted, one end connected to charging current reference 108 and transistor 106, and its source connected to power supply voltage 119. The gate of transistor 106 is connected to one end of transistor 105, its source connected to power supply voltage 119, and its drain connected to switch 104.

[0025] Exponentially rising current 117 is formed by the drain currents of transistors 101 (second) and 110 (fifth). Transistors 114 (seventh) and 115 (eighth) form current amplification group 116, which amplifies the exponentially increasing current. The current amplitude of 117 is amplified to the final exponentially increasing current. 118. Transistor 7 (114) has its drain and gate shorted, one end connected to the drains of transistors 2 (101) and 5 (110), and transistor 8 (115). Its source is connected to the power supply voltage. 119. One end of transistor 8 (115) is connected to transistor 7 (114), and its drain current is the exponentially increasing current of the final output. 118, the source is connected to the supply voltage 119. Constant current reference 112 provides a current reference for constant current group 113, time-dependent current reference 107 provides a current reference for time-dependent current group 109, and charging current reference 108 provides a current reference for time-dependent current group 109. Transistors 100, 101, 110, and 111 are all NMOS transistors, while transistors 105, 106, 114, and 115 are all PMOS transistors. Therefore, the final output current... 118 represents the source current. All transistors operate in the saturation region.

[0026] The working principle of the exponentially rising current generating circuit is as follows: Initially, all switches 103-104 are in the open state, and the current output is... 117 is determined by constant current group 113, and at this time it is a constant current.

[0027] When switch 103 is closed, current is output. 117 is determined by constant current group 113, time-dependent current reference 107, transistor 100 and transistor 2 101, and is a constant current at this time.

[0028] The required current output range is determined based on the application, and the final output current is controlled by the ratio between transistor 7114 and transistor 8115. The initial output current of 118. The final output current at this point. 118 is shown below (here, the input and output multipliers of the current mirror in time-dependent current group 109 and constant current group 113 are set to 1, and the size and physical parameters of each transistor in time-dependent current group 109 and constant current group 113 are kept consistent). and (Reference currents output by time-dependent current reference 107 and constant current reference 112, respectively). = ; ; It can be seen that the output current I1117 of the time-dependent current group 109 and the constant current group 113 consists of a constant term and an exponential function. The sign before the independent variable t in the exponential function is positive, indicating that the current generated by the circuit increases with time, thus yielding a current that increases exponentially with time.

[0029] Will and We can obtain the following by replacing the current and voltage equations of NMOS transistors 2101 and 5110 operating in the saturation region: These are characteristic parameters of a transistor. and These are the gate voltages of transistor 5110 and transistor 2101. (This refers to the transistor's turn-on voltage). ; ; With switch 103 open, and since capacitor 102 stores charge, the gate voltage of transistor 101 in time-dependent current group 109 remains constant, and the current supplied by time-dependent current group 109 remains constant. The final output current... 118 also remains unchanged.

[0030] When switch 104 is closed, the charging current reference 108 begins to affect the time-dependent current group 109. Charge is injected into capacitor 102 through the charging current reference 108, transistor 105, and transistor 106. The gate voltage of transistor 101 increases continuously over time.

[0031] At this time, the output currents of time-dependent current group 109 and constant current group 113 are... 117 represents the exponentially increasing current that rises continuously with time, obtained through the Taylor approximation scheme, i.e., the exponentially increasing current ( The reference current output by the charging current reference 108 is the reference current. (This is the capacitance value of capacitor 102) ; Depending on the given current reference, the circuit... It is greater than Both are constants, and since the physical parameters of transistor 101 and transistor 110 are exactly the same, and The difference is also a constant, let's assume this constant is... By substituting these values ​​into the calculation, we can obtain: ; It can be seen that the output current of time-dependent current group 109 and constant current group 113 is an exponentially increasing current. 117 consists of a constant term and an exponential function. The independent variable in the exponential function... The preceding sign is positive, indicating that the current generated by the circuit increases with time, that is, the current increases exponentially with time.

[0032] Exponentially rising current 117 is formed by the drain currents of transistors 101 (second) and 110 (fifth). Transistors 114 (seventh) and 115 (eighth) form current amplification group 116, which amplifies the exponentially increasing current. The current amplitude of 117 is amplified to the final exponentially increasing current. 118. Transistor 7 (114) has its drain and gate shorted, one end connected to the drains of transistors 2 (101) and 5 (110), and transistor 8 (115). Its source is connected to the power supply voltage. 119. One end of transistor 8 (115) is connected to transistor 7 (114), and its drain current is the exponentially increasing current of the final output. 118, the source is connected to the power supply voltage 119. This results in a current output at the... With 118, you can obtain an exponentially rising current waveform with a wider output range, less susceptibility to temperature, lower power consumption, faster response speed, and longer pulse time.

[0033] Based on the aforementioned technical solution, the circuit structure was built in Cadence using the 0.18μm process provided by SMIC (Semiconductor Manufacturing International Corporation). Simulation methods verified that the design of the above structure has high feasibility.

[0034] The circuit simulation structure is based on Figure 1 The timing steps for setup and simulation are consistent with the above-described process, at the circuit output terminal. 118 continuously monitors the output current. The pulse width of the exponentially rising waveform can be calculated based on the current magnitudes of capacitor 102, charging current reference 108, and the current difference between constant current reference 112 and time-dependent current reference 107. Observing the output waveform, the waveform deviates by 25% between -40℃ and 80℃. However, between 0℃ and 50℃, the exponentially rising waveform using the subthreshold scheme deviates by 473%. By introducing the current difference between constant current reference 112 and time-dependent current reference 107, the pulse width of the exponentially rising waveform can be more than doubled.

[0035] The comparative results show that the circuit structure of the present invention has good stability, can adapt to a wider range of temperature changes, and has lower power consumption, faster response speed and wider output range.

[0036] Therefore, the present invention provides an improved exponentially rising waveform generation circuit for nerve electrical stimulation with the above-described structure, which has a larger output range and can meet the needs of the biomedical field for inducing neural activity; at the same time, due to the larger output range, the pulse width of the exponentially rising current waveform is extended, which can ensure that the neurostimulator can work stably in more medical fields; it has a faster response speed and lower power consumption compared with the exponentially rising current generation circuit based on a pure current scheme; under the influence of temperature, the exponentially rising current waveform changes less, which can be applied to a wider range of biomedical application scenarios.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An improved exponentially rising waveform generation circuit for nerve electrical stimulation, characterized in that: It includes a constant current group (113), a time-dependent current group (109), and an amplified current group (116). The constant current group (113) consists of transistor five (110) and transistor six (111) and is used to provide the constant term in the expression for the exponentially rising current formed by the Taylor approximation; the drain and gate of transistor six (111) are shorted and connected to the constant current reference (112); the gates of transistor five (110) and transistor six (111) are connected and their sources are all grounded (120); the drain current of transistor five (110) and the drain current of transistor two (101) form an exponentially rising current. (117); The constant current reference (112) is connected to the power supply voltage (119); The time-dependent current group (109) consists of transistor 1 (100), transistor 2 (101), capacitor (102), switch 1 (103), switch 2 (104), transistor 3 (105), and transistor 4 (106), and is used to provide the rising term in the expression of the exponentially rising current formed by the Taylor approximation; the drain and gate of transistor 1 (100) are shorted, one end is connected to the time-dependent current reference (107) and switch 1 (103), and the source is connected to ground (120); the drain current of transistor 2 (101) and the drain current of transistor 5 (110) constitute the exponentially rising current. (117), the gate is connected to switch one (103), switch two (104) and capacitor (102), and the source is connected to ground (120); one end of capacitor (102) is connected to one end of switch one (103), switch two (104) and transistor two (101), and the other end is connected to ground (120); one end of switch one (103) is connected to transistor one (100), and the other end is connected to switch two (104), transistor two (101) and capacitor (102); switch two (104) One end of the transistor is connected to one end of switch one (103), transistor two (101) and capacitor (102), and the other end is connected to one end of transistor four (106); the drain and gate of transistor three (105) are shorted, one end is connected to the charging current reference (108) and transistor four (106), and the source is connected to the power supply voltage (119); the gate of transistor four (106) is connected to one end of transistor three (105), the source is connected to the power supply voltage (119), and the drain is connected to switch two (104); The amplifying current group (116) is composed of transistor seven (114) and transistor eight (115) and is used to amplify the exponentially rising current generated by the constant current group (113) and the time-dependent current group (109). (117) Amplification is performed to generate the final exponentially increasing current. (118); The drain and gate of transistor seven (114) are shorted, one end of which is connected to the drain of transistor two (101) and transistor five (110) and transistor eight (115), and the source is connected to the power supply voltage (119); one end of transistor eight (115) is connected to transistor seven (114), and the drain current is the exponentially increasing current of the final output. (118) The source is connected to the power supply voltage (119). The constant current reference (112) provides a current reference for the constant current group (113); the time-dependent current reference (107) provides a current reference for the time-dependent current group (109); and the charging current reference (108) provides a current reference for the time-dependent current group (109).

2. The improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: Transistors 1 (100), 2 (101), 5 (110), and 6 (111) are all NMOS transistors, while transistors 3 (105), 4 (106), 7 (114), and 8 (115) are all PMOS transistors. The final output exponentially increasing current... (118) is the traction current.

3. The improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: Transistor 1 (100), transistor 2 (101), transistor 3 (105), transistor 4 (106), transistor 5 (110), transistor 6 (111), transistor 7 (114) and transistor 8 (115) all operate in the saturation region.

4. The improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: The current value of the charging current reference (108) is several orders of magnitude smaller than that of the constant current reference (112) and the time-dependent current reference (107) so as to slowly inject charge into the capacitor (102) through the charging current reference (108) to increase the gate voltage of transistor two (101) and increase the final exponentially rising output current. (118) exponentially increasing current pulse width.

5. An improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: The time-dependent current reference (107) and the constant current reference (112) are not equal; the constant current reference (112) is greater than the time-dependent current reference (107) to increase the final exponentially rising output current. (118) exponentially increasing current pulse width.

6. An improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: Switch 1 (103) and switch 2 (104) are both transistor switches, which are turned on and off according to the gate voltage to facilitate chip integration and digital control.

7. An improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: The size and physical parameters of the transistors constituting the current mirror in the time-dependent current group (109) and the constant current group (113) can be set according to actual needs.

8. An improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: The amplifying current group (116) controls the exponentially rising current of the final output through the ratio between transistor seven (114) and transistor eight (115). The magnitude of the initial output current of (118) thus expands the output range of the exponentially rising current by several times.

9. An improved exponentially rising waveform generation circuit for nerve electrical stimulation according to claim 1, characterized in that: Its generation method includes the following steps: S1. Initially, all switches are in the open state, and the current output increases exponentially. (117) is determined by the constant current group (113), and the output is a constant current at this time; S2, Close switch one (103), the current output current increases exponentially. (117) is determined by the constant current group (113), the time-dependent current reference (107), transistor one (100) and transistor two (101), and is a constant current at this time; S3. Determine the required current output range based on the application, and use the ratio between transistor seven (114) and transistor eight (115) to control the exponentially increasing current of the final output. The magnitude of the initial output current of (118), and the exponentially increasing current of the final output. (118) As shown below, select the current mirror input and output multipliers of 1 in the time-dependent current group (109) and the constant current group (113), where and The reference currents output by the time-dependent current reference (107) and the constant current reference (112) are respectively: = ； ； Will and The equations are obtained by replacing them with the current-voltage equations of NMOS transistors 2 (101) and 5 (110) operating in the saturation region, where These are characteristic parameters of a transistor. and The gate voltages of transistors 5 (110) and 2 (101) are, The turn-on voltage of the transistor: ； ； S4. Disconnect switch one (103). Since capacitor (102) stores charge, the gate voltage of transistor two (101) in time-dependent current group (109) remains unchanged, and the current supplied by time-dependent current group (109) remains unchanged, resulting in an exponentially increasing output current. (118) Remain unchanged; S5. When switch two (104) is closed, the charging current reference (108) begins to affect the time-dependent current group (109). Charge is injected into capacitor (102) through the charging current reference (108), transistor three (105), and transistor four (106). The gate voltage of transistor two (101) increases continuously over time. At this time, the output current of the time-dependent current group (109) and the constant current group (113) increases exponentially. (117) is the exponentially increasing current that increases continuously with time, obtained through the Taylor approximation scheme, i.e., the exponentially increasing current, where The reference current output by the charging current reference (108) is the reference current. Here is the capacitance value of capacitor (102): ； Depending on the given current reference, the circuit... Greater than Both are constants, and since the physical parameters of transistor 2 (101) and transistor 5 (110) are completely identical, and The difference is also a constant, and this constant is assumed to be... And by substituting the values ​​into the calculation, we get: ； This yields a current that increases exponentially with time. After being amplified by the current amplification group (116), the current at the output terminal increases exponentially. (118) The final exponentially rising current waveform is obtained.

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