JPH0964698A - Oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generates a saw tooth wave synchronous with a synchronizing signal by inputting the same synchronizing signal as a signal outputted from a differential amplifier to a buffer. SOLUTION: A synchronizing circuit 5 inputs a synchronizing signal having the same value as a signal outputted from the differential amplifier 1 from an external device to the buffer 2. The circuit 5 is constituted of a pnp transistor (TR) Q6, npn TR Q7 and a current source 15. The emitter of the TR Q7 and the current source 15 are conneced in series between a power supply Vcc and a ground power supply and a synchronizing signal is inputted to the base of the TR Q7. The TR Q6 connects its base to a node between the TR Q7 and the current source 15, connects its emitter to the base of an npn TR Q3 and connects its collector to the ground. If an external synchronizing signal falls when a capacitor C1 is charged with electricity from the current source 14, an npn TR Q2 is turned off and discharge from the capacitor C1 is started. Thereby the base voltage of an npn TR Q1 falls, the TRs Q1, Q5 are turned off and the TR Q2 is turned on, starting charging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator that can be synchronized with an external device.

[0002]

2. Description of the Related Art A conventional oscillator is shown in FIG. In the figure, reference numeral 1 is a differential amplifier, and 2 is a first buffer, which inputs a signal from a negative output terminal of the differential amplifier 1 to a negative input terminal of the differential amplifier 1. A second buffer 3 receives a signal from the + side output terminal of the differential amplifier 1. A sawtooth wave generation circuit 4 charges and discharges a signal from the second buffer 3, generates a sawtooth wave by charging and discharging, and inputs the sawtooth wave to the + side input terminal of the differential amplifier 1.

The differential amplifier 1 is composed of resistors R1, R2, NPN transistors Q1 and Q2, and a current source I1 between a power source Vcc and a ground power source. The NPN transistor Q1 has a base as a + side input terminal and a collector as a − side output terminal. And the collector is a resistor R
1 and the emitter is connected to the current source I1. NPN
The base of the transistor Q2 serves as the negative (-) side input terminal,
The collector serves as the + output terminal. The collector is connected to the resistor R2 and the emitter is connected to the current source I1.

The buffer 2 includes an emitter of an NPN transistor Q3, a resistor R3, and a resistor R3 between a power source Vcc and a ground power source.
A current source I2 is connected in series to form a configuration. Resistor R1 and NPN
The connection point of the collector of the transistor Q1 is connected to the base of the NPN transistor Q3. Resistor R3 and current source I
The connection point with 2 is connected to the base of the NPN transistor Q2.

The buffer 3 includes an emitter of the NPN transistor Q4, a resistor R4, and a resistor R4 between the power source Vcc and the ground power source.
A current source I3 is connected in series to form a configuration. Resistor R2 and NPN
The connection point between the collector of the transistor Q2 and the base of the NPN transistor Q4.

In the sawtooth wave generating circuit 4, a current source I4 and a capacitor C1 are connected in series between a power source Vcc and a ground power source, and an NPN transistor Q5 is connected in parallel with the capacitor C1.
Is provided. The connection point between the resistor R4 and the current source I3 is NP
Connected to the base of N transistor Q5. Current source I4
The connection point between the capacitor and the capacitor C1 is the NPN transistor Q1.
Connect to the base of.

The operation of such a device will be described below.
Here, for the voltage value of the power supply, the current value of the current source, and the resistance value of the resistor, the same symbols as those used for the current source and the resistor are used. Further, the base-emitter voltage of the transistor Qi is set to "Vbei". In the initial state, the voltage between the terminals of the capacitor C1 is “0V”, the NPN transistor Q1 is in the off state,
The NPN transistor Q2 is turned on and the NPN transistor Q5 is turned off.

Since the NPN transistor Q2 is off, both NPN transistors Q4 and Q5 are off.
The capacitor C1 is charged by the current source I4. The base voltage of the NPN transistor Q1 is equal to the base voltage of the NPN transistor Q2 "Vcc- (Vbe3 + I2.R).
3) ", the NPN transistor Q1 is turned on and the NPN transistor Q2 is turned off. At the same time, the base voltage of the NPN transistor Q2 is" Vcc ".
-(I1 · R1 + Vbe3 + I2 · R3) ”.
Since the PN transistor Q2 is turned on, the discharge of the capacitor C1 starts, and the terminal voltage of the capacitor C1 drops to "Vcc- (I1.R1 + Vbe3 + I2.R3)". As a result, the NPN transistor Q1 is turned off, the NPN transistor Q2 is turned on, the NPN transistor Q5 is turned off, and the charging of the capacitor C1 is started again. In this way, a sawtooth wave is generated by the terminal voltage of the capacitor C1.

[0009]

However, in such a structure, there is a problem in that the synchronization signal from the external device and the sawtooth wave cannot be synchronized.

Therefore, an object of the present invention is to realize an oscillator capable of synchronizing with a synchronizing signal of an external device.

[0011]

According to the present invention, there is provided a differential amplifier, and a first buffer for inputting a signal from a negative output terminal of the differential amplifier to a negative input terminal of the differential amplifier.
A second buffer for inputting a signal from the + side output terminal of the differential amplifier and a signal from the second buffer are charged / discharged, a sawtooth wave is generated by the charge / discharge, and the sawtooth wave is generated. A sawtooth wave generation circuit input to the + side input terminal of the dynamic amplifier, and a synchronizing signal having the same value as the signal output from the differential amplifier in the first buffer or the second buffer. By inputting, a sawtooth wave synchronized with the synchronizing signal is generated.

[0012]

In the present invention as described above, the synchronizing signal having the same value as the signal output from the differential amplifier is input to the first buffer or the second buffer. As a result, the sawtooth wave generation circuit generates a sawtooth wave in synchronization with the synchronization signal.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. Hereinafter, the same parts as those in FIG. 3 are designated by the same reference numerals. In the figure, 5
Is a synchronization circuit, which inputs a synchronization signal having the same value as the signal output from the differential amplifier 1 to the buffer 2 from an external device (not shown). The synchronizing circuit 5 includes PNP transistors Q6 and N.
It is composed of a PN transistor Q7 and a current source I5. The emitter of the NPN transistor Q7 and the current source I5 are connected in series between the power source Vcc and the ground power source, and the synchronization signal is input to the base of the NPN transistor Q7. The PNP transistor Q6 has a base connected to the connection point of the NPN transistor Q7 and the current source I5, an emitter connected to the base of the NPN transistor Q3, and a collector connected to the ground.

The operation of such a device will be described below.
FIG. 2 is a timing chart for explaining the operation of the device shown in FIG. In the initial state, the voltage between the terminals of the capacitor C1 is "0.
V ″, the NPN transistor Q1 is off, the NPN transistor Q2 is on, the NPN transistor Q5 is off, and the voltage value of the synchronizing signal is “Vcc”.

In the initial state, the capacitor C1 is connected to the current source I
Charged by 4. At this time, when the sync signal from the external device falls from "Vcc" to "Vcc-I1.R1", the emitter voltage of the PNP transistor Q6 changes from "Vcc" to "Vcc-I1.multidot.R1" via the NPN transistor Q7.
As a result, the base voltage of the NPN transistor Q2 is "Vcc- (Vbe3 + I2.R3)" which is "V".
cc- (Vbe3 + I2 ・ R3 + I1 ・ R1) ”, and N
The PN transistor Q2 changes from the ON state to the OFF state, and at the same time, the NPN transistor Q1 changes from the OFF state to the ON state. When the NPN transistor Q1 is turned on,
The NPN transistor Q4 also changes from the off state to the on state, and the base voltage of the NPN transistor Q5 becomes "Vcc-
(Vbe5 + I3 · R4 + I1 · R2) ”to“ Vcc-
(Vbe5 + I3 · R4) ”, and the state changes from the off state to the on state. Then, the charge stored in the capacitor C1 starts to be discharged. As a result, the NPN transistor Q
Although the base voltage of 1 increased, it started to decrease. The terminal voltage of the capacitor C1 (base voltage of the NPN transistor Q1) is "Vcc- (I1.R1 + Vbe3 + I2.R).
3) ″, the NPN transistor Q1 is turned off, the NPN transistor Q2 is turned on, the NPN transistor Q5 is turned off, and the capacitor C1 is charged again until the synchronizing signal falls. Repeatedly, a sawtooth wave is generated by the terminal voltage of the capacitor C1.

As described above, since the synchronizing signal having the same value as the signal output from the differential amplifier 1 is input to the buffer 2, the sawtooth wave generating circuit 4 can generate the sawtooth wave synchronized with the synchronizing signal.

The present invention is not limited to this, and the following may be used. The synchronizing circuit 5 only functions as a buffer, and may have a configuration in which the synchronizing signal is input to the buffer 2 without going through the synchronizing circuit 5. The buffers 2 and 3 have the resistors 3 and 4, but may not be provided. Although the configuration in which the synchronization signal is input to the buffer 2 has been shown, the configuration in which the synchronization signal is input to the buffer 3 also allows the sawtooth wave generation circuit 4 to generate a sawtooth wave in synchronization with the synchronization signal.

[0018]

According to the present invention, since the synchronizing signal having the same value as the signal output from the differential amplifier is input to the first buffer or the second buffer, the sawtooth wave generating circuit synchronizes with the synchronizing signal. There is an effect that a sawtooth wave can be generated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the device of FIG.

FIG. 3 is a diagram showing a configuration of a conventional oscillator.

[Explanation of symbols]

 1 differential amplifier 2 3 buffer 4 sawtooth wave generation circuit 5 synchronization circuit

Claims (1)

[Claims] 1. A differential amplifier, a first buffer for inputting a signal from a negative output terminal of the differential amplifier to a negative input terminal of the differential amplifier, and a positive buffer for the positive side of the differential amplifier. A second buffer for inputting a signal from the output terminal, and charging and discharging by the signal from the second buffer, a sawtooth wave is generated by the charging and discharging, and the sawtooth wave is applied to the + side input terminal of the differential amplifier. In the oscillator having a sawtooth wave generation circuit for inputting to the first synchronization buffer, a synchronization signal having the same value as the signal output from the differential amplifier is input to the first buffer or the second buffer. An oscillator characterized by generating a synchronized sawtooth wave.