JPS5843299Y2 - Trapezoidal wave generation circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a trapezoidal wave generation circuit, and an object of the present invention is to generate a stable trapezoidal wave with equal rising and falling edges and little fluctuation.

FIG. 1 shows the principle of a conventional trapezoidal wave circuit, which is a type of trapezoidal wave.

Resistors 1 and 2 determine the bias, resistor 3 determines the constant current value, and transistor 4 operates to charge the capacitor 5 with the constant current determined by resistor 3.

The resistor 6.7 determines the bias, the resistor 8 determines the constant current value, and the transistor 9 operates to discharge the constant current determined by the resistor 8 from the capacitor 5.

Reference numerals 10 and 11 are switches for alternately charging and discharging, and terminal 12 is a DC voltage source.

This circuit charges the capacitor 5 with a constant current 1 when the switch 10 is closed and the switch 11 is open, and discharges the constant current I2 from the capacitor 5 when the switch 11 is closed and the switch 12 is open. .

Now, set the resistance values of resistors 1, 2, 3, 6, 7.8 to each R1s
R2wR3*R6*R7*RB, transistor 4,
If hFE of 9 is ignored, constant current ■1. ■2 becomes, but since there are two supply circuits for constant current ■ and ■2, when integrated into a semiconductor circuit, resistors 1, 2, 3,
Due to the variation between 6 and 7.8, the constant current ■1
It became difficult to set I2 and I2 to the same value.

The present invention solves the above problems by extracting the charging current and the discharging current from one supply circuit, and by configuring a trapezoidal wave generating circuit that can easily obtain a trapezoidal wave with equal rise and fall. An embodiment thereof will be described below with reference to the drawings.

FIG. 2 shows the basic configuration of the trapezoidal wave generating circuit according to the present invention.

2, terminal 13 is a DC voltage source, and link 1
4 is a terminal to which a constant voltage is applied.

15.16 indicates a switch, transistor 17.18
indicates a differential amplifier.

19 indicates a constant current source, and 20 indicates a constant current circuit.

The capacitor 21 is a capacitor for charging and discharging.

Now, by alternately applying the voltage p and current applied from the terminal 14 to the base of the differential amplifier consisting of the transistors 17 and 18 by the switches 15 and 16, when the transistor 17 is turned on, its collector current 2 becomes If hFo of the transistor 17 is sufficiently thick, then the following equation is obtained.

The current (3) is determined by a circuit configuration that can flow a current that is the same as or proportional to the collector current (2) of the transistor 17.

Now, the current ■3 is the collector current ■2 of the transistor 17.
If you configure the circuit so that the current value is the same as (2)
The current charged to the capacitor 21 by the formula ■3 is) ■3=11 ・・・・・・・・・・・・・・・
......(3).

When the transistor 18 is in the ON state, the discharge current ■ is as follows, and if the hFE of the transistor 18 is sufficiently large, I4 = 11...
......(5).

According to equations (3) and (5) above, the collector current of the transistor 17 ■2 and the current charging the capacitor 21 ■
By configuring the circuit so that they have the same current value, charging current ■3 and discharging current ■4 are calculated as ■3=■4
・・・・・・・・・・・・・・・・・・・・・
(6) becomes.

Therefore, it is possible to always make the charging current I3 and the discharging current ■4 equal.

FIGS. 3 and 4 show a trapezoidal wave generating circuit diagram and a waveform diagram of its connection points according to an embodiment of the present invention.

In FIG. 3, 22 is a DC power supply terminal.

Resistors 23, 24, 25, 26.27 and diodes 28.
29 and transistor 30 are bias supply parts for applying to the base of a differential amplifier composed of transistors 31 and 32.

Due to the configuration of resistors 33 and 34 and transistors 35, 36, and 37, the transistor 31 of the differential amplifier is
．． 32 are operated alternately.

A resistor 39 is a resistor that determines the constant current value.

Transistors 40, 41 and 42 constitute a constant current circuit,
43 is a charging and discharging capacitor.

A transistor 44 and a resistor 45 are used to output an output to an output terminal 46.

Now, regarding this circuit configuration, biases vb and (2) applied to the bases of transistors 31 and 32 constituting the differential amplifier.

For example, the input signal applied from the input terminal 38.

When the level is W (sufficiently lower than VBE), transistors 35 and 36 are turned off and transistor 3T is turned on.

vb and V at that time are vbt and V.

If it is 1, ■e1 =O・・・・・・・・・・−・
・・・・・・(7)Vbl ””Va VBE
・・・・・・・・・・・・・・・・・・(8)

On the other hand, when the input signal applied from the input terminal 38 is at Hi level (sufficiently higher than VBE), the transistor 35
．． 36 is in the ON state, and the transistor 37 is in the QFF state.

If Vb and Vc at that time are Vb2,\ve2 ””Va VBE...
・・・・・・・・・・・・(9)■5゜=O・・・・・・
・・・・・・・・・・・・(10)

From the above formulas (7L (8), (9), and (io)), the input signal applied from the input terminal 38 is:

When the level is W, the transistor 31 of the differential amplifier is O.
It becomes N state and 32 becomes OFF state.

Furthermore, when the input signal is at Hi-level, the transistor 31 of the differential amplifier becomes a QFF state, and the transistor 32 becomes an ON state.

Now, resistors 23 and 24.39 are R23°R24 and R3 respectively.
9, the emitter bias 4 of the differential amplifier transistors 31 and 32 is Vd:vcl-BE:Vb
2-VBE V8-2VBE ・・・・・・・・・・・・・・・・・・
········(11) The connection point bias ■8 between the resistor R23 and the diode 28 is as follows.

According to (ii) and equation (12), becomes.

The current (1) flowing through the transistors 31 and 32 is as follows.

PNP) depending on the configuration of transistors 40, 41, and 42,
The current (2) flowing to the collector of the transistor 31 and the current (3) charging the capacitor 43 (if PNP) are equal if the hFE of the transistors 40, 41, 42 are sufficiently large, so the charging current I3 and the discharging current (4) are as follows. becomes.

Therefore, if the capacitance of the capacitor 43 is CH, then the rise time t1 and the fall time t2 of the trapezoidal output waveform are equal.

Therefore, regardless of changes in Va due to variations between resistors 23 and 24 and changes in constant current (1), charging current (3) and discharging current (4) are always equal, so the rise time t1 and fall of the trapezoidal wave output It is always equal to time t2.

As described above, the present invention alternately applies a constant voltage source to the base of a differential amplifier consisting of a first transistor and a second transistor using a switch, and generates a current equal to the current flowing through the collector of the first transistor. , or by connecting a circuit carrying a proportional current between the collector of the second transistor and the power supply, connecting a capacitor to this connection point, and charging and discharging the same current or a proportional current through the switch, A trapezoidal wave whose rise and fall times are equal or proportional can be easily and stably generated.

[Brief explanation of drawings]

Figure 1 is a schematic circuit configuration diagram of a conventional trapezoidal wave generation circuit;
The figure is a basic configuration diagram of the trapezoidal wave generation circuit according to the present invention.
The figure is a trapezoidal wave generating circuit diagram of an embodiment of the present invention, and FIG. 4 is a waveform diagram of each part of the circuit of FIG. 3. 1s, 16... Switch, 23, 24, 25° 26.27, 39.45... Resistance, 31.32
...Transistor constituting a differential amplifier, 35
, 36° 37...Transistor, 40.41.
...transistor constituting a constant current circuit, 43.
...Charging and discharging capacitor.

Claims (1)

[Scope of utility model registration request] It has a differential amplifier configured by connecting a constant current circuit to the common emitters of the first transistor and the second transistor, and the bases of both transistors are connected to a constant voltage source through a switch, respectively. A current mirror circuit that flows a current equal to the current flowing through the collector of the transistor is connected between the differential amplifier and the power supply, and a capacitor is connected between the connection point between the current mirror circuit and the second transistor of the differential amplifier and ground. is connected, and by applying an input signal to the switch, the second transistor is alternately turned on and off to cause photodischarge of the capacitor via the constant current circuit and the current mirror circuit, and the input signal is output from the capacitor. A trapezoidal wave generation circuit is characterized in that it obtains a trapezoidal wave according to.