JPS6057613B2 - integral circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to an integrating circuit with improved input/output characteristics.

A conventional integrating circuit is shown in FIG.

1 is an input terminal, 2 is a switch for starting integration, 3 is a switch for resetting the integral value, 4 is an inverting amplifier, 5 is an output terminal, R is an integrating resistor, and R is an integrating resistor.

is a reset resistor, and Cl is a capacitor. In this case, if switches 2 and 3 are replaced with semiconductor analog switches (for example, transistors), the integral output will be limited by the power supply voltage. Therefore, if it is desired to obtain an integrated output voltage greater than the power supply voltage value VCc1 of the semiconductor analog switch, a circuit configuration as shown in FIG. 2 is required. That is 6
is an input terminal, 7 is a semiconductor analog switch, 8 is for integration, 9 is for reset, 10 is an inverting amplifier, 11 is a common mode amplifier, 12 is an output terminal, R3 is an integrating resistor, R,
is a reset resistor, and C2 is an integrating capacitor.
Then, Vccl is applied to the semiconductor analog switch 7 and the inverting amplifier 10, and VcC2 is applied to the in-phase amplifier 11 as a power supply. ±VCC2 is set higher than VCCI in order to obtain the desired output voltage, and the voltage gain of the common-mode amplifier 11 is set larger than Vcc2/Vcl, so that the common-mode amplifier 11 clips faster than the inverting amplifier 10. (saturation). With this configuration, even when the output 12 reaches the desired output value within +Vcc2A), the output of the inverting amplifier 10 is still within ±VcCl, so the semiconductor analog switch 7 will not operate abnormally. do not have. If we keep the configuration shown in Figure 1 and simply convert switches 2 and 3 to analog, the inverting amplifier 4
When the power supply voltage is increased, a high voltage is applied to the switch 3, causing abnormal operation. Therefore, in an integrating circuit using a semiconductor analog switch, if the power supply voltage of the semiconductor analog switch is limited and you want to obtain an integrated output higher than the power supply voltage, an amplifier is used as shown in Figure 2. I have no choice but to add 11. The object of the present invention is to provide an integrating circuit which can be constructed from a simple circuit without adding such an amplifier, and which satisfactorily achieves the above object without causing malfunction.

In other words, in an integrating circuit that feeds back from the output terminal of an amplifier such as an inverting amplifier to the inverting input terminal through an impedance such as a capacitor, the output of the amplifier is divided by a resistor and fed back to the inverting input terminal, and when holding, the feedback is A reset circuit is provided to prevent this. Third
The figure shows an example of a circuit according to the invention.

13 is a terminal for inputting the signal to be integrated into the integrating circuit;
Reference numeral 4 indicates a switch for starting integration, 15 indicates a switch for resetting the integral value, and 16 indicates that the start switch 14 and the reset switch 15 are constituted by semiconductor analog switches.

17 is an inverting amplifier, and 18 is an output terminal.

R5 is an integrating resistor, R6 and R7 are reset resistors,
C3 is an integrating capacitor that feeds back the output of the amplifier 17 to the inverting input. The power supply voltage VCC2 applied to the inverting amplifier 17 is set to be sufficiently large in order to obtain the desired output voltage at the output 18.

The reset signal is divided by resistors R6 and R and fed back to the inverting input terminal of the amplifier. Even if the signal is divided and returned in this way, the purpose of resetting is sufficiently achieved. Moreover, even if a sufficiently large integrated output is output from the amplifier, it is divided, so that even if the power supply voltage of the analog switch is low, no abnormal operation will occur. If the division ratio of R6 and R7 is selected here, optimal operation will be achieved.

The integrator circuit configured in this way will only fail even if the output voltage at the output terminal 18 reaches the maximum VCC2. Since only a voltage lower than VCCl is fed back to the division point of R7 and R7, the semiconductor analog switch 16 will not operate abnormally. In this circuit example, as examples of element constants, ±■Cc=±12V, ±■CC2=±24V,
R6=4.7K, R7=3.9K, R5=100KΩ,
Very good results were obtained using C3=4.7 μF.

As described above, in the present invention, the output of the integrating circuit is divided and fed back for resetting the integral value, so even if the reset switch is configured with a semiconductor analog switch, it is not possible to obtain an integral output higher than the power supply voltage of the analog switch. can.

[Brief explanation of drawings]

Figures 1 and 2 are conventional integration circuit diagrams, and Figure 3 is an integration circuit diagram according to the present invention. In the figure, 17 is an amplifier, R5 and C3 are integral elements, 15 is a reset switch, and R6 and R7 are for reset. It is a split resistance.

Claims (1)

[Claims] 1 In an integrating circuit configured by feeding back the output of an amplifier to the inverting input via an impedance such as a capacitor, the divided output of the amplifier's output is fed back to the inverting input of the amplifier, and the feedback is blocked during hold. An integrating circuit characterized by being provided with a reset circuit.