JPS581469B2 - signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal generating device that generates a hyperbolic function signal or a signal proportional to the logarithm of a hyperbolic function, which is constructed of a capacitor and a semiconductor device.

Conventionally, circuits that use capacitors and resistors to generate signals that change linearly or logarithmically over time have been widely put into practical use, but the accuracy of generating signals that are proportional to the hyperbola of time or the logarithm of the hyperbola is There was no suitable circuit with a high value.

The present invention makes it possible to obtain a hyperbolic function signal or a signal proportional to the logarithm of a hyperbolic function by skillfully utilizing the characteristics of a semiconductor device having a capacitor and a junction. Shown below.

In FIG. 1, 1 is a capacitor, and 2 is a semiconductor device connected to the capacitor 1. Here, a diode-connected transistor is shown as an example.

In this circuit, the capacitor 1 and the semiconductor device 2 are
The capacitor 1 is connected so that the potential difference e of the capacitor 1 is equal to the potential difference of the semiconductor device 2, and so that a current proportional to the current flowing through the capacitor 1 flows through the semiconductor device.

Now, a DC voltage Es is applied to the capacitor 1 via the switch S.
When S is opened after applying , the current i flowing through the capacitor 1 (here the same as the current flowing through the semiconductor device 2) and the voltage e applied to the semiconductor device 2 (here the same as the potential difference of the capacitor 1) are respectively It is expressed by equations (1) and (2).

However, C: Capacitance of capacitor 1 k: Boltzmann constant T: Junction surface temperature of semiconductor device g: Electronic charge Ieo: Reverse current of semiconductor device Eliminating e from equations (1) and (2) gives (3 ) formula is obtained.

In equation (3), if i (o)=io, this singular solution is as shown in equation (4).

In equation (4), since kTC/q and kTC/qio are both constant values, the current i flowing through the capacitor becomes a hyperbolic function with respect to time t, as shown in FIG.

In addition, the voltage e applied to the semiconductor device 2 can be calculated by converting equation (4) into (2
), it becomes clear that the signal is proportional to the logarithm of the hyperbolic function.

FIG. 3 is a tangent diagram when the signal generator shown in FIG. 1 is applied to a circuit that converts a frequency signal into a voltage signal.

In the figure, 30 is a terminal to which a pulse train signal sf of frequency f to be converted is applied, as shown in FIG. 4A, for example;
M1 is a monostable multivibrator triggered by this pulse train signal sf, which generates a sampling pulse PS1 as shown at the beginning of FIG.

M2 is a monostable multivibrator triggered by PS1, which generates a drive pulse PS2 of frequency f for driving switch S as shown in FIG. 4C.

When the switch S is driven by the driving pulse PS2 for a period of Δt (Δt is determined by the circuit constant of the monostable multivibrator M2), a charging current as shown in FIG. 4D flows through the capacitor 1 during this period. .

When the switch S is turned off, the current flowing through the capacitor 1, that is, the current i flowing through the semiconductor device 2, becomes a hyperbolic function signal as shown in equation (4) (see the waveform in FIG. 4D).

This signal is applied to the input end of an operational amplifier OP having a feedback resistor Rf, and a signal ey as shown in equation (5) can be obtained from its output end.

However, Rf: resistance value of the feedback resistor Rf T0: period of the pulse signal to be converted In equation (5), the time Δt and/or i0 for which the switch S is turned on is as shown in the equation.

As is clear from equation (6), the output signal ey of the operational amplifier op has a value proportional to the frequency f to be converted.

The sample and hold circuit SH1 samples this signal ey with a sampling pulse Ps1 synchronized with the next input pulse, and outputs a signal to the output terminal 31 as shown by the broken line e0 in FIG. 4, which is proportional to the inverse of the pulse interval T0, that is, the frequency f. Outputs a voltage signal like this.

Further, the sample and hold circuit SH2 samples the potential difference of the capacitor 1 and outputs a signal proportional to the logarithm of the frequency f to the output terminal 32.

Conventionally, there is a circuit that converts a frequency signal into a voltage signal using a triangular wave signal obtained by constant current charging and short-circuit discharging of a capacitor, such as the one described in Japanese Patent Publication No. 14393/1983. In order to obtain a signal proportional to frequency, a reciprocal conversion operation must be performed.

According to the circuit shown in FIG. 3 using the signal generating device according to the present invention, a signal proportional to frequency can be instantaneously obtained without performing reciprocal conversion operations.

5 to 9 are connection diagrams showing other embodiments of the device of the present invention.

The device shown in FIG. 5 uses a diode as the semiconductor device 2.

The device shown in FIG. 6 uses a transistor whose base is grounded as a semiconductor device 2, and a capacitor 1 and this transistor are connected between the input and output terminals of an operational amplifier OP0.

The device shown in FIG. 7 uses a base-emitter junction of a transistor as a semiconductor device, and extracts a current β times the current i flowing therethrough as a collector current i.

The device shown in FIG. 8 uses a gate-source junction of an FET as a semiconductor device, and extracts a current i' which is gm times the voltage V as a drain current.

In this case, the drain current i' becomes a signal proportional to the logarithm of the hyperbolic function.

The device shown in FIG. 9 uses a diode-connected transistor as a semiconductor device, connects a capacitor 1 between the input and output terminals of an operational amplifier OP0, and sets the output voltage of the operational amplifier OPo, that is, the voltage of the capacitor 1, to a variable resistor
v1 is set to 1/n1, and this voltage v/n1 is applied to the semiconductor device 2. Also, the current i flowing through the semiconductor device 2 is set to 1/n2 by variable resistor Rv2, and this current i
/n2 is made to flow into capacitor 1.

As described above, according to the present invention, it is possible to realize a device that can obtain a hyperbolic function signal or a signal proportional to the logarithm of a hyperbolic function with high accuracy using an extremely simple circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing one embodiment of the device of the present invention, FIG. 2 is an explanatory diagram of the operation of the device of FIG. 4 is an explanatory diagram of the operation of the circuit shown in FIG. 3, and FIGS. 5 to 9 are connection diagrams showing other embodiments of the device of the present invention. DESCRIPTION OF SYMBOLS 1... Capacitor, 2... Semiconductor device, S... Switch means, SH1, SH2...
...Sample hold means, M1, M2...
... Monostable multivibrator.

Claims (1)

[Scope of Claims] 1. A semiconductor device having a capacitor, a junction having at least one end connected to the capacitor, a switch means for applying a constant voltage to the capacitor, and a semiconductor device for applying a constant voltage to the capacitor for a predetermined time by the switch means. and a signal extraction circuit for extracting a signal related to a current flowing through the semiconductor device and/or a potential difference between the capacitors, and a bipolar line function signal or a signal proportional to the logarithm of the bipolar line function is obtained from the signal extraction circuit. signal generator. 2. The signal generating device according to claim 1, wherein a diode is used as the semiconductor device, and the diode is connected in parallel to a capacitor. 3. The signal generating device according to claim 1, wherein a transistor whose base is grounded is used as the semiconductor device, and a capacitor is connected in parallel to this transistor. 4. The signal generating device according to claim 1, wherein a base-emitter junction of a transistor is used as the semiconductor device, and a capacitor is connected between the base and emitter. 5. The signal generating device according to claim 1, wherein a gate-source junction of an FET is used as the semiconductor device, and a capacitor is connected between the gate and source. 6. The signal generating device according to claim 1, which uses a diode-connected transistor as the semiconductor device. 7. A semiconductor device having a capacitor, a junction having at least one end connected to the capacitor, and a switch means for applying a constant voltage to the capacitor for each input pulse;
a signal extraction circuit that extracts a signal related to the current flowing through the semiconductor device and/or the potential difference of the capacitor after applying a constant voltage to the capacitor for a predetermined period of time by the switch means; A signal generating device comprising sample and hold means for sampling in synchronization, and obtaining a signal proportional to the reciprocal of the pulse interval of the input pulse and/or the logarithm of the reciprocal of the pulse interval from the output end of the sample and hold means.