Wide-range current-to-frequency converter专利检索-电容分压器分压器控制系统专利检索查询-专利查询网

Wide-range current-to-frequency converter

阅读：94发布：2021-07-06

专利汇可以提供Wide-range current-to-frequency converter专利检索，专利查询，专利分析的服务。并且Improved wide-range current-to-frequency converter for analogto-digital conversion of low-level signals in a simple, lowpower, self-zeroing circuit utilizing capacitive feedback, which virtually eliminates the effects of voltage offsets at the input of the converter while avoiding large leakage currents, without the need for complicated and bulky range-changing switches, external zeroing using either automatic or manual techniques, or preceding electrometer amplifiers, includes a low-leakage chargesensitive amplifier, a gated multivibrator, a charge pulser and a capacitive divider. The gated multivibrator under the control of the charge-sensitive amplifier at the input of the converter produces discrete pulses, which in turn cause the charge pulser to generate discrete units of charge, which are reduced in magnitude by the capacitive divider to become the charge-feedback pulses applied to the input of the charge-sensitive amplifier. This amplifier compares the feedback current consisting of repetitive charge-feedback pulses with the input current to the converter, and controls the gated multivibrator so that the pulse repetition rate varies in an appropriate manner to keep the feedback current equal to the instantaneous value of the input current, resulting in the repetition frequency of the gatedmultivibrator pulses becoming a digital representation of the analog input current. This technique can provide a dynamic range of 107:1 and can handle input currents as small as 10 14 A directly without preceding electrometer amplifiers, and it also provides a mechanism for discharging the capacitive divider in a manner such that the circuit automatically establishes its own zero level.，下面是Wide-range current-to-frequency converter专利的具体信息内容。

权利要求

1. For use in combination in a circuit capable of quantizing small currents, an improved wide-range current-to-frequency converter comprising: a. amplifier means, adapted to receive an input current having a signal current and repetitive discrete feedback charge pulses, for providing a comparison between the charge arising from the signal current and the total discrete feedback charge, and for producing an output voltage proportional to the difference between the total feedback charge and the total charge produced by the signal current; b. charge-generating means, connected to the output of the amplifier means, for producing known amounts of charge at a charge output whenever the amplifier means indicates that the feedback charge has a smaller absolute magnitude than the input charge, and for producing at those times frequency output pulses whose repetition rate becomes an output frequency signal; and c. capacitive-divider means, connected between the charge output of the charge-generating means and the input to the amplifier means, for attenutating the charge generated by the chargegenerating means, to produce said repetitive discrete feedback charge pulses; whereby, analog-to-digital conversion is accomplished by producing a train of pulses at the frequency output with a repetition frequency related in a known way to the signal current applied to the input of the current-to-frequency converter.

2. The circuit of claim 1, above, further comprising a pulse-generating means connected to the charge-generating means, said pulse-generating means producing pulses which cause the capacitive-divider means to be discharged in such a fashion that the current-to-frequency converter establishes its own zero level, permitting operation over a wide range of input currents.

3. The circuit of claim 1, above, wherein the feedback charge is fixed and constant so that the output frequency of the converter is proportional to the input current.

4. The circuit of claim 1, above, wherein the converter measures linearly input currents between 3 X 10 14A and 1.8 X 10 7A.

5. The circuit of claim 1, above, wherein the converter measures linearly input currents between 3 X 10 14A and 1.8 X 10 7A, corresponding to input charges between 3.6 X 10 14C and 2.4 X 10 8C for 1.2-s integration intervals.

6. The circuit of claim 1, above, wherein said amplifier means comprises a charge-sensitive amplifier having offset currents, input voltages and noise, which generate negligible errors in relation to threshold signals applied to the converter.

7. The circuit of claim 1, above, wherein said amplifier means comprises a MOSFET in its input stage.

8. The circuit of claim 1, above, wherein the value of the capacitive division provided by said capacitive-divider means can be changed in order to extend the dynamic range of the converter.

9. The circuit of claim 1, above, wherein said capacitor-divider means comprises high-resistivity, low-leakage capacitors to reduce leakage currents at the converter input.

10. The circuit of claim 9, above, wherein said capacitor-divider means provides for the attenuation of leakage-current effects arising in the charge-generating means.

11. The circuit of claim 1, above, wherein said charge-generating means comprises gated-multivibrator means and charge-pulser means, connected to the gated-multivibrator means.

12. The circuit of claim 11, above, wherein said charge-pulser means comprises a circuit for changing the voltage across a capacitor in defined, discrete steps under the control of an external signal.

13. The circuit of claim 11, above, wherein said charge-pulser means produces positive charges under the control of one external signal and negative charges under the control of another external signal.

14. The circuit of claim 11, above, wherein said charge-pulser means produces a charge with its polarity controlled by one external signal, with the time of occurrence of the charge pulse being determined by a second external signal.

15. The circuit of claim 11, above, wherein said charge-pulser means provides for charging a capacitor in defined, discrete steps under the control of an external signal and also provides for discharging said capacitor rapidly under the control of a second external signal.

16. The circuit of claim 11, above, wherein said gated-multivibrator means comprises a circuit for producing a pulse with a fixed width whenever a control signal falls below the threshold voltage for a defined length of time.

17. The circuit of claim 16, above, wherein said gated-multivibrator means produces a train of output pulses with a defined minimum pulse separation whenever the control signal remains constantly below the threshold voltage.

18. The circuit of claim 11, above, wherein said charge-pulser means comprises: a. a transistor operated in the grounded-base mode with its collector connected to the output terminal of the charge-pulser means; b. a coupling capacitor connected to the emitter of said transistor for providing charge pulses upon command by an external signal; and c. a diode connected between the emitter and the base of the transistor with the opposite polarity as the emitter-base junction of the transistor, whereby charge pulses are produced at the output terminal of the charge pulser whenever the external signal causes the coupling capacitor to be charged through the emitter of the transistor after said coupling capacitor has been discharged through the diode.

19. The circuit of claim 18, above, further comprising a second transistor of opposite polarity to the grounded-base transistor connected between the output terminal of the charge pulser and a defined voltage, said second transistor permitting an additional external signal to switch the output terminal of the charge pulser to a defined voltage by saturating said second transistor.

20. The circuit of claim 16, above, wherein said charge-pulser means provides for a varying charge output by changing the magnitude of the external signal and by changing the value of the coupling capacitor.

21. The circuit of claim 18, above, further comprising an inverter with a variable reference voltage, connected to the coupling capacitor and the external signal, said inverter, upon command by the external signal, producing voltage steps with a magnitude controlled by the variable reference voltage.

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Wide-range current-to-frequency converter

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