JPS5845850B2 - Kukeihanohakouchigen Cairo - Google Patents

Description

Detailed Description of the Invention The present invention provides a rectangular wave peak value limiting circuit that limits a rectangular wave having a constant level to a rectangular wave having a peak value corresponding to a control input signal having an arbitrary voltage level. It is related to.

For impedance conversion (buffer), for example,
An emitter follower using a transistor as shown in Japanese Patent No. 6-15190 is used.

The emitter follower has an input voltage ■IN that responds to temperature changes.
Even if is O, the emitter voltage vBE is -2mV/℃
Since the emitter output voltage Von
t also has a temperature characteristic of about -2 mV/°C.

Therefore, the only way to improve the temperature characteristics is to compensate for this in other parts, which makes the circuit complicated.

An object of the present invention is to obtain a rectangular wave peak value limiting circuit with a simple configuration and less temperature characteristics in order to obtain a rectangular wave having a peak value corresponding to a control input signal having an arbitrary voltage level. .

For this reason, the configuration of the present invention includes a voltage follower circuit made of an operational amplifier, and a switching circuit made of a transistor whose collector is connected to the output side of the voltage follower circuit via a resistor, and the input side of the voltage follower circuit is A voltage for controlling the peak value of a rectangular wave is applied to the transistor, a reference rectangular wave is applied to the base side of the transistor of the switching circuit, and a rectangular wave having a peak value corresponding to the control voltage is obtained from the collector side. This is what I did.

To explain the configuration of the present invention based on an embodiment, in FIG. 1, 1 is a voltage follower circuit consisting of an operational amplifier 8 and a resistor 9, and 3 is a control with an arbitrary voltage level that limits the peak value of a rectangular wave. A voltage input terminal 6 is an output terminal of the voltage follower circuit 1.

2 is a switching circuit consisting of a transistor 13 and a resistor 10°11.12; 4 is an input terminal for a rectangular wave with a constant voltage level; and 5 is an output terminal for a rectangular wave with a peak value limited to an arbitrary voltage level. .

In FIG. 2, ■ is a rectangular wave having an O level and an E level, and is applied to the terminal 4.

2 is a control voltage having the level of Vc, which is applied to the terminal 3.

3 is a rectangular wave having the O level and the Vc level, and is output from the terminal 5 with the wave height limited to the peak value Vc.

In the above circuit configuration, the terminal 3 is connected to Vo as shown in ■.
When a voltage having a level of is applied to the terminal 6, since the operational amplifier 8 forms a voltage follower at the terminal 6, the same voltage level Vc is obtained.

Then, when a rectangular wave having an O level and an E level as shown in ■ is applied to the terminal 4, the transistor 13 of the switching circuit 2 is non-conductive while the level of the rectangular wave shown in I is O. Therefore, a voltage at the level of Vc can be obtained.

Since the transistor 13 is conductive while the level of the rectangular wave is E, the level becomes O.

Eventually, a rectangular wave having an O level and a Vc level is obtained as shown in (3).

In the present invention, since the transistor 13 is used with saturation amplification, the collector voltage VOE when the transistor 13 is in a conductive state can be suppressed to about 20 to 30 mV, and this voltage VOR has a temperature characteristic. Even so, it's not a problem.

This is because, in the case of saturated amplification, the temperature characteristic of the emitter voltage VOE is generally about +0.5%/°C of the voltage VOE, so if the voltage VOE is 20 to 30 mV,
Temperature characteristics are 100~150μV/'C (0.1~0.1
5TrLVloC), which is more than one order of magnitude smaller than the temperature characteristic of the base voltage VBE in the case of an emitter follower.

As described above, according to the present invention, it is possible to provide, at a low cost, a peak value limiting circuit for an digit wave with good power supply utilization rate, temperature characteristics, and the like.

[Brief explanation of the drawing]

FIG. 1 is an electrical wiring diagram of a peak value limiting circuit according to the present invention, and FIG. 2 is an input/output waveform of the circuit. 1... Voltage follower circuit, 2...
・Switching circuit, 8... Operational amplifier, 13
...Transistor.

Claims (1)

[Claims] 1 A voltage follower circuit consisting of an operational amplifier, and a switching circuit consisting of a transistor whose collector is connected to the output side of the voltage follower circuit via a resistor, and the peak value of a rectangular wave is input to the input side of the voltage follower circuit. A rectangular waveform is characterized in that a voltage to be controlled is applied, a reference rectangular wave is applied to the base side of the transistor of the switching circuit, and a rectangular wave having a peak value corresponding to the control voltage is obtained from the collector side. Wave peak value limiting circuit.