JPS6267921A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To reduce the number of externally mounted capacitors and externally mounted pins in the formation of IC by applying constant current charge/ discharge of a capacitor in response to the collector current of the 1st and 2nd TRs connected differentially so as to generate a triangle wave output signal at a capacitor. CONSTITUTION:A capacitor 18 is connected to a base of the 2nd TR 17 in the 1st and 2nd TRs 16, 18 connected differentially. In applying a power supply +Vcc and the initial charge of the capacitor 18 is assumed as zero since the base voltage of the TR 17 is zero, the TR 16 is turned on and the TR 17 is turned off just after the application of power. Then TRs 23, 24, 25 are turned on, the capacitor 18 is charged by the collector current of the TR 25. When the constant current charging of the capacitor 18 is propressed and its terminal voltage reaches the base voltage of the TR 16, the TRs 17, 26 start the turning on and TRs 27, 31, 29 and 30 are turned on. Thus, the electric charge in the capacitor 18 is discharged through a constant current through the collector- emitter path of the TR 30.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an oscillation circuit, and more particularly to an oscillation circuit suitable for a caltone signal generation circuit used in setting the recording level of a tape recorder.

(b) Conventional technology In order to obtain a triangular wave signal, as shown in Figure 2, an astable multivibrator (1) is used to create a square wave signal, and an integrator circuit (2) is used to generate the square wave signal. ) and integrate it. Usually 5 astable multi-noise ibrators (1
), a monomer as shown in FIG. 3 is used. Third
In the figure, the first and second transistors (3) and (4
) has the first and second capacitors (5) and (
6) The collectors and bases of the first and second transistors (3) and (4) are connected to the power supply (10 Vcc) through the first to fourth resistors (7) to (IO+V), respectively. ) The astable multivibrator connected to the It is conventionally known. Therefore, the oscillation frequency f1 of the astable multivibrator described in vI, f −□ ・・・・・・・・・・・・・・・・・・
......(1)' 1.39CbRb. Let us find the values of the first and second capacitors (5) and (6) based on the above equation (1). Heat generation frequency f1
When the frequency is set to 400Hz and the values of the second and third resistors (8) and (9) are respectively set to 20Ω, the values of the first and second capacitors (5) and (6) are respectively 0.09 μF.
become. On the other hand, the cutoff frequency f of the integrating circuit (2) is 5, and the oscillation circuit is -5d1 from the cutoff frequency f.
It has a frequency characteristic that drops at 310ct. It should be noted that the closed loop gain AMP is given by Rr/R (where Rf is the resistance value of the resistor α), so it is expressed by the above equation (2).

The integration circuit (2) performs an integration operation.

Since the frequency is higher than the cutoff frequency 17, the capacitance cf of the capacitor 02) when a 400Hz square wave signal is applied to the integrating circuit (2) is equal to the cutoff frequency f2 times 40
Hz, if the resistance circle value Rf is 100 and Ω, then 0.0
It becomes 4μF.

(・→ The problem that the invention seeks to solve Generally speaking, IC (
The capacitance of a capacitor that can be made into an integrated circuit (integrated circuit) is several hundred pF. Therefore, astable multivibrator (1)
The first and second capacitors (5) and (6) that make up the circuit, as well as the capacitor that makes up the integrating circuit (2) (as it is not possible to convert the Sakura into an IC, and the coupling capacitor 05) are also required. When converting the circuit shown in Figure 1 into an IC, there are problems in that the number of external capacitors increases and the number of terminal pins of the IC also increases.

(2) Means for Solving Problems The present invention 1 has been made in view of the above-mentioned points, and includes first and second transistors that are differentially connected, and a transistor that is connected to the base of the second transistor. A capacitor, a charging circuit that charges the capacitor with a constant current in response to the collector DC of the first transistor, and a discharging circuit that discharges the capacitor with a constant current in response to the collector current of the second transistor (M). It is characterized by points.

(E) Function According to the present invention, by performing constant current charging and discharging tV of the capacitor according to the collector currents of the first and second transistors connected differentially, a triangular wave output signal is generated at one end of the capacitor. Therefore, it is possible to reduce the number of external capacitors and external pins when implementing an IC.

(j Example) FIG. 1 shows an example of the present invention, in which 06) and α7) are differentially connected first and second transistors, a
A capacitor connected to the base of the second transistor a7), α9 is connected to the base of the first and second transistor (16
1 and (I7), a wL source connected to the common emitter of
■, (2I) and (22 are the first, second and third resistors connected in series between the power supply (10cc) and the ground, (23
) & the third +- transistor of the diode-connected type connected to the collector of the first transistor OFA; a fourth transistor;
25) in order to charge the capacitor marked 0,
A fifth transistor (26)' is connected to the transistor (23) by an α current mirror, and (26)' is connected to the second transistor (17).
) is a diode-connected sixth transistor connected to the collector of the transistor (26), @', L is a seventh transistor that is current mirror-connected to the @6 transistor (26), and ■ is the discharge tV of the eighth transistor and the capacitor a barrel. The collector of the seventh transistor (2'7) consists of the ninth transistor country and the collector of the seventh transistor (2'7)! Ma inverting current mirror circuit and 01)
are the fourth and fifth transistors (24), CI! In order to forcibly drive (2), a tenth transistor is connected to the sixth transistor (2G) as a current mirror. Note that the base of the first transistor (LD) is connected to the second and third resistor series υ and @
It is connected to the connection point of the capacitor (18), one end I of the capacitor (18), and the runaway terminal (three terminals).

Next, I will explain the operation. When you turn on the power (+■cc),
The base voltage of the first transistor (161 is
and a third resistor (20), CI! 1) and (resistance value of 221), and the base voltage of the capacitor (second transistor 07) will be zero if the initial charge of the capacitor is zero.

Immediately after the power is turned on, the first transistor (16) is turned on and the second transistor σ is turned off. When the first transistor (16) turns on, the third transistor (16) turns on.
(c) is turned on, and the fourth and fifth transistors (24) and (c) are also turned on. When the fifth transistor C25+ is turned on, its collector current charges the capacitor.
? On the other hand, when the fourth transistor (2) is turned on, the first resistor wire is short-circuited, so the first transistor (Vel□t is the collector-emitter saturation of the fourth transistor (24) voltage).

In this state, the capacitor (
As the constant current charging for 1 second progresses, the terminal voltage of the capacitor α barrel becomes equal to the base voltage of the first transistor aω.
η starts to be on, and accordingly, the sixth transistor (a) also starts to be on. When the sixth transistor 06) is turned on, the seventh and tenth transistors C31)6' connected to the current mirror are turned on, and in response to the turning on of the seventh transistor 06), the eighth transistor C31) is turned on, forming a current mirror circuit.
And the ninth transistor (to) is turned on. Therefore, the charge at 0 seconds of the capacitor is 0 at the 9th transistor in I.
) is discharged with a constant current through the collector-emitter path.

On the other hand, when the tenth transistor 1) turns on, the base voltages of the fourth and fifth transistors (24) and (c) rise, forcing the fourth and fifth transistors t24) and □□□ to turn off. Driven. When the fourth transistor (24) is turned off, the short circuit of the first resistor (20) is released, so that the first transistor is lowered and turned off.

As the discharge of the capacitor α barrel by the 9th transistor (to) progresses and the base voltage of the 2nd transistor η drops to the 1st level, the @1 transistor (1θ is turned on again and the second transistor (17) is turned off. , the fifth transistor (C) is also turned on, so constant current charging of the capacitor (1al) is restarted.Therefore, constant current charging and constant current discharging of the capacitor (18) are repeated, and the output terminal 2 is A triangular wave oscillation output signal can be obtained.

When implementing the oscillation circuit in Figure 1 into an IC, if each transistor is sufficiently matched, the value of the charging current by the fifth transistor (c) and the value of the discharging current by the ninth transistor (to) can be made to match. This makes it possible to match the photoelectric time and discharge time. Therefore, it is possible to obtain a triangular wave with good linearity and a clean waveform. In addition, the capacitor (switching from the discharging state marked with 1 to the charging state is
This is facilitated by the positive feedback operation of increasing the collector current of the transistor, increasing the collector current of the third transistor (c), increasing the collector current of the fourth transistor, and increasing the base voltage of the first transistor (L6). Since the switching from the charging state to the discharging state is facilitated by the tenth transistor Gυ, the switching time can be short-circuited.

Furthermore, consider the frequency f of the oscillation circuit shown in FIG.

Capacitor (charge Q of IQ is Q=CV ・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・(4)

Also, the collector of the capacitor 08 & the fifth transistor ■■ is Kiryuko. Since it is being charged at a constant current, Q21゜t・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・(51) Therefore, the time t until the terminal voltage V of the capacitor (l mallet) is, and the 1 oscillation frequency f is , The values of the capacitance C1 of the capacitor α marked I, the values of the second and third resistors Cυ and (2) can be set accurately.
4) Collector φ emitter voltage■. meat can also be kept constant. Therefore, the power supply voltage +■. By keeping f constant, the oscillation frequency f can be kept constant, and a stable output signal can be obtained. In addition, if the value of the current flowing through the current source (19) connected to the common emitter of the first and second transistors 0Q and σD is adjusted by an external resistor, The value of . can be changed, and the oscillation frequency can be arbitrarily set. Since the number of external capacitors and the number of external pins can be reduced, it is possible to provide an oscillation circuit suitable for IC implementation.Furthermore, it is possible to adjust the current flowing to the DC source connected to the emitters of the first and second transistors. Ba.

An oscillation circuit having an arbitrary oscillation frequency can be provided.

Therefore, the oscillation circuit according to the present invention is suitable for use in generating caltone signals for tape recorders.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional triangular wave generation oscillation circuit, and FIG.
′! , is a circuit diagram showing an example of the astable multivibrator. Explanation of main drawing numbers α6)...1st transistor, a7)...2nd transistor, bet...capacitor, (e)...5th transistor, (5)...fIX7 transistor,
(To)...9th transistor.

Claims (1)

[Claims] (1) first and second transistors that are differentially connected; a capacitor connected to the base of the second transistor;
a charging circuit that charges the capacitor at a constant current according to the collector current of the first transistor; and a discharging circuit that discharges the capacitor at a constant current according to the collector current of the second transistor; An oscillation circuit characterized by generating an output signal.