JPS5922989B2 - signal generator - Google Patents

Description

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

The applicant of the present application has already proposed a signal generating device that can 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.

The principle diagram is shown in Fig. 1. In FIG. 1, 1 is a capacitor, and 2 is a semiconductor device connected to the capacitor 1. Here, a diode-connected transistor is illustrated.

The semiconductor device may be a diode with a PN junction.

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 3.
When switch 3 is opened after giving
i and the voltage e applied to the semiconductor device 2 (here, the same as the potential difference of the capacitor 1) are expressed by equations (1) and (2), respectively.
) is expressed by the formula.

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

If 1(o)=io in equation (3), this singular trace becomes as shown in equation (4).

Since kTC/q and kTc/qio in equation (4) are both constant values, the current i flowing through the capacitor 1 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 an electrical circuit diagram of a signal generation device that applies the device in FIG. .

In the drive pulse generation circuit 10, 11 is a terminal to which a pulse train signal Sf of frequency fn as shown in FIG. This generates a sampling pulse PS1 as shown in FIG.

Reference numeral 13 is a monostable multi-bi break triggered by PSl, and a driving pulse PS with a frequency fn as shown in FIG.
2.

In the hyperbolic function signal generation circuit 20, the switch 22.
23 is driven by the drive pulse PS2 for a time Δt (Δt is determined by the circuit constant of the monostable multi-bibreak 13), the capacitor 1 receives the constant current i of the constant current source 21 during this time.

charged by.

When the switches 22 and 23 are turned off, the current flowing through the capacitor 1, that is, the current i flowing through the semiconductor device 2, is
This results in a hyperbolic function signal as shown by equation (4).

This signal is applied to the input terminal of an operational amplifier 24 having a feedback resistor 25 with a resistance value R, and after a time Tn-Δ, a signal Etn as expressed by equation (5) can be obtained from its output terminal. .

however, n: 1, 2, 3.・・・・・・ Tn: Period of pulse train signal In equation (5), when switches 22 and 23 are on, TC If the time △t is set in the relationship △t-7, then qt.

Equation (5) is as follows.

As is clear from equation (6), the hyperbolic function signal Etn output from the operational amplifier 24 has a value proportional to the frequency fn.

In the sample hold circuit 30, the hold circuit 32
is the sampling pulse PSI synchronized with the next input pulse
The hyperbolic function signal Etn sampled by the sampling switch 31 driven by
A voltage signal Eon as shown by the broken line in Figure E is output.

Note that if the potential difference of the capacitor 1 is sampled and held in synchronization with the sampling pulse PS1 as described above, a voltage signal proportional to the logarithm of the frequency fn can be obtained.

Conventionally, a circuit for obtaining a voltage signal corresponding to a frequency signal has been designed to sample and hold the amplitude of a triangular wave signal obtained by constant current charging and short-circuit discharging of a capacitor, as described in Japanese Patent Publication No. 51-14393. However, in such a circuit, a reciprocal conversion operation must be performed in order to obtain a signal proportional to the frequency.

According to the signal generator shown in FIG. 3, a signal proportional to the frequency or a signal proportional to the logarithm of the frequency can be immediately obtained without performing a reciprocal conversion operation.

Now, in the apparatus shown in FIG. 3, when the frequency fn of the pulse train signal Sf changes, the output voltage signal Eon changes stepwise as shown by the broken line in FIG. 6E.

The present invention reduces the frequency of the applied pulse train signal by adding a simple circuit to the device of FIG.

In other words, an attempt was made to realize a signal generating device in which the output voltage signal does not change stepwise but continuously follows and decreases the hyperbolic function signal of time when the period changes in the direction of increasing length.

FIG. 4 is an electrical circuit diagram showing an embodiment of the signal generating device according to the present invention, in which comparing means 40 consisting of an analog comparator 41 and an OR gate 42 is added to the device shown in FIG.

The analog comparator 41 outputs the output signal of the operational amplifier 24, that is, the hyperbolic function signal E, only when the strobe STR, which is the page output of the monostable multi-bi break 13, is established.
tn and the value held by the hold circuit 32, that is, the output signal Eon
When Etn>Eon, logic "101', E
When tn≦Eon, an output signal CMP of logic "1" is generated.

The OR gate 42 performs an OR combination with the output signal CMP of the analog comparator 41 and the sampling pulse PS1 generated by the monostable multi-bi break 12, and sends out a drive signal PS3 for driving the sampling switch 31.

The operation of the signal generator of the present invention in such a configuration will be explained as follows.

In synchronization with the pulse train signal Sf, the capacitor 1 is charged and discharged similarly to the device shown in FIG. 3, and the operational amplifier 24 outputs a signal Etn as shown at hot in FIG. 6.

In this case, the drive pulse PS2 shown in FIG. 6C falls,
When the capacitor 1 starts discharging, the step STR is established as shown in FIG. 62, and the analog comparator 41 starts a comparison operation.

That is, the output signal of the operational amplifier 24, that is, the hyperbolic function signal Etn, and the output signal Eo corresponding to the frequency one cycle before.
Start comparison with n.

When the frequency fn of the pulse train signal Sf fluctuates in the increasing direction, Etn>Eon (n=1.2.3) as seen in ranges ■, ■, and ■ in Figure 6 (e), so the analog comparator The discrimination signal CMP 41 is always at the II L I+ level as shown in FIG.

This discrimination signal CMP is ORed with the sampling pulse PS1 by an OR gate 42.

As a result, the sampling switch 31 is driven only by the sampling pulse PS1, and E o 1 occurs in a stepwise manner as shown by the broken line in FIG. 6E.
Output signals Eon such as s Eo2 and E o 3 are obtained.

Next, when the frequency fn of the pulse train signal Sf fluctuates in a decreasing direction as shown in the range ① to ② in FIG. 6, the following occurs.

That is, as shown in FIG. 6E, when the hyperbolic function signal Et4 generated in the range ■ gradually decreases with time and matches the output signal E o 4 corresponding to the frequency f3 one cycle before at time t4, the discrimination signal CMPl/i As shown in Figure 6, I
It becomes I HIf level.

As a result, the OR gate 42 outputs an output signal of II HI+ level and turns on the sampling switch 31.

In this manner, after time t4, the sampling switch 31 remains on, and the hold circuit 32 continuously follows and outputs the hyperbolic function signal Et4.

In other words, the output signal E O4 of the hold circuit 32 is at time t
Before time t4, it shows a constant value Eo4, and after time t4, it stays at a hyperbolic waveform a as shown in FIG. 6E and decreases.

When the next pulse of the pulse train signal Sf arrives and the sampling pulse PS1 is emitted, the hold circuit 32 that sends out the output signal Eon that changes in this way holds and outputs the final value Eo5 of the hyperbolic function signal at that time. .

In this way, it is possible to obtain an output signal Eon that continuously follows the hyperbolic function signal and decreases.

Note that in the embodiment, the output signal Etn of the operational amplifier 32 is given to the sample-and-hold circuit 30, but if the potential difference of the capacitor 1 is given to the sample-and-hold circuit 30, the signal generator can obtain an output signal according to the logarithm of the frequency. , and its output signal can decrease following the logarithm of the hyperbolic function in the same way as described above.

FIG. 5 shows an on/off switch 52 driven by a diode 51 and a strobe STR in the comparison means 40 of the device shown in FIG.
The cathode of the diode 51 is connected to the hyperbolic function signal generating circuit 20.
The anode is connected to the input end of the hold circuit 32 via an on/off switch 52.

In such a configuration, as is clear from FIGS. 6E and 6, the intermittent switch 52 is turned on by the strobe STR while the hyperbolic function signal Etn is being generated.

As a result, since the input terminal of the hold circuit 30 is diode-connected to the output terminal of the hyperbolic function signal generation circuit 20, the input terminal potential of the hold circuit 30 is pulled by the output terminal potential of the hyperbolic function signal generation circuit 20 and decreases. do.

In this way, it is possible to obtain an output signal Eon that continuously decreases following the hyperbolic function signal Etn.

As explained above, according to the signal generator of the present invention,
A hyperbolic function signal Et decreasing according to a hyperbolic function of time
n is compared with the held value corresponding to the frequency one cycle before, that is, the output signal Eon, and when the former becomes smaller than the latter, it is possible to generate an output signal Eon that continuously follows the former and decreases.

In particular, if the signal generating device of the present invention is used in a frequency meter or tachometer equipped with an indicating instrument, and the indicating instrument is driven by the output signal of the device of the present invention, the pointer of the indicating instrument will move smoothly without vibration. There are advantages.

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing the principle device of the present invention, Fig. 2 is an explanatory diagram of the operation of the device shown in Fig. 1, and Fig. 3 is a signal generation by applying the device shown in Fig. 1 to obtain a voltage signal corresponding to a frequency signal. FIG. 4 is an electric circuit diagram showing one embodiment of the signal generating device according to the present invention, and FIG. 5 is an electric circuit diagram showing another embodiment of the signal generating device according to the present invention. FIG. 6 is an operational waveform diagram of each part in FIGS. 3 to 5. DESCRIPTION OF SYMBOLS 1...Capacitor, 2...Semiconductor device, 3...Switch, 10...Drive pulse generation circuit, 20...Hyperbolic function generation circuit, 3
0... Sample hold circuit, 31...
- Sampling switch, 32... Hold circuit, 40... Comparison means, 41... Analog comparator, 42... OR gate, 5
0...Simple comparison means, 51...Diode, 52...Intermittent switch.

Claims (1)

[Scope of Claims] 1. A semiconductor device having a capacitor and a PN junction, a switch means for applying a charging current to the capacitor for each pulse of a pulse train signal, and a potential difference in the capacitor and a potential difference in the semiconductor device are proportional to each other, and a hyperbolic function signal generation circuit that connects a capacitor and a semiconductor device so that a current proportional to the current flowing through the capacitor flows through the semiconductor device, and obtains a hyperbolic function signal corresponding to the current that changes in proportion to a hyperbolic function of time; A signal generating device comprising a sample and hold circuit that samples the hyperbolic function signal in synchronization with the pulse train signal, and in which an output signal corresponding to the frequency of the pulse train signal is obtained from an output end of the sample and hold circuit. The present invention is characterized by comprising a comparison means for comparing the magnitude of the signal and the output signal of the sample and hold circuit, and when the hyperbolic function signal becomes smaller than the output signal, the output signal follows the hyperbolic function signal. Signal generator. 2. The comparing means comprises an analog comparator that compares the hyperbolic function signal and the output signal, and an OR gate that OR gates the discrimination signal generated by the analog comparator and the sampling pulse synchronized with the pulse train signal, and Claim 1, characterized in that the sample and hold circuit is constituted by a sampling switch driven by the output signal of the OR gate and a hold circuit.
Signal generator as described in section. 3. The sample and hold circuit includes a sampling switch and a hold circuit driven in synchronization with the pulse train signal, and the comparison means includes an intermittent switch that is driven and turned on only during the period when the hyperbolic function signal is generated. 2. The signal generating device according to claim 1, comprising a diode connected in series to an intermittent switch and connected in parallel to said sampling switch.