JPS61224514A - Astable multivibrator - Google Patents

Abstract

PURPOSE:To obtain an oscillation output with a stable frequency against a power supply voltage and temperature by supplying a voltage of a resistor deciding the oscillating frequency and a reference voltage of a voltage comparator deciding the oscillation amplitude from one power supply. CONSTITUTION:Charge/discharge of a capacitor C0 is repeated between reference voltages Emax and Emin, a flip-flop 3 repeates set/reset and a rectangular oscillation output is obtained at a terminal T5. When the current density of transistors Q1, Q10 is equal, the oscillation period t0 is expressed as t0=(2 C0R0)(R2+R3)/n(R1+R2). That is, the oscillating frequency or period depends only on elements R1-R3, C0, R0, and a current ratio (n) of the current mirror circuit 4 and is independent of the power supply voltage Vcc and temperature. Thus, the elements R0, C0 are mounted externally and selected as components with sufficient accuracy and stability, then the highly accurate and stable oscillation output is obtained at a desired oscillation frequency.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an astable multivibrator.

[Summary of the invention]

This invention improves various characteristics of an unstable multi-pipe rake by supplying the resistor voltage that determines the oscillation frequency and the reference voltage of the voltage comparator circuit that determines the oscillation amplitude from the same power source. .

[Conventional technology]

An unstable multivibrator as shown in FIG. 3 or 4 is known as an oscillation circuit.

[Problem that the invention seeks to solve]

However, in the circuit shown in Figure 3, in order to stabilize the oscillation frequency, the discharge current of the capacitor Ca, which determines the oscillation frequency, must be 100 times or more than the charging current, and the discharge period Tb of the capacitor Ca is set as shown in Figure 5. needs to be sufficiently short compared to the charging period Ta. However, if this is done, the discharge current of the capacitor Ca becomes a spike wave, resulting in large noise.

In this respect, in the circuit shown in FIG. 4, the terminal voltage of capacitor cb, which determines the oscillation frequency, is as shown in FIG. 6, and little noise is generated.

However, in this circuit, in order to reduce the frequency change with respect to temperature, the potential at point A must be reduced to 2XVBI! Since it is necessary to stabilize the voltage at 2XVBIE and is limited to 2XVBIE, the circuit for stabilization cannot be shared with other circuits. Also, precision is required for the capacitor cb and resistor Rh that determine the oscillation frequency, so if this circuit is integrated into an IC, the elements Cb and Rh must be externally connected.
terminals (bins) are required, which is disadvantageous for IC implementation.

This invention attempts to solve the above problems.

[Means for solving problems]

This invention improves the characteristics of an unstable multi-pipe rake by supplying the resistor voltage that determines the oscillation frequency and the reference voltage of the voltage comparator circuit that determines the oscillation amplitude from the same power supply. .

[Effect]

According to the present invention, since power supply voltage, temperature, etc. are not included in the equation giving the oscillation frequency or oscillation period, it is possible to obtain an oscillation output with a stable frequency with respect to the power supply voltage, temperature, etc. Further, all variables in the equation giving the oscillation frequency or oscillation period can be made more accurate by externally attaching the elements Ro and Co, so that a highly accurate oscillation frequency can be obtained.

Furthermore, since the oscillation frequency or oscillation period is not affected by voltage, there is no need to prepare a constant voltage circuit, which is advantageous for IC implementation. Further, the terminals necessary for externally attaching the elements Ro and Co are terminals T3. There are two T4 pieces,
From this point of view as well, the benefits of IC implementation remain intact. Moreover,
Changes in the charging and discharging current of the capacitor CO are smooth and do not generate spike noise.

〔Example〕

In FIG. 1, resistors R1 to R3 and the collector terminal of transistor Q1 are connected between power supply terminal T1 and ground terminal T2.
The emitters are connected in series, and the base of the transistor Q1 is connected to the midpoint between the resistors R2 and R3.
The midpoint of the connection between the resistors R1 and R2 and the collector of the transistor Q1 are connected to the inverting input terminals of the voltage comparison circuits (11, (21), and their output terminals are connected to the RS flip-flop (3).
) is connected to the set terminal S and reset terminal R of the terminal.

In addition, a current mirror circuit (4) is configured by transistors Q+o and Qu, with terminal T2 as a reference potential point and transistor Q+o as an input terminal.
The collector of so is connected to terminal T3. For example, by making the emitter junction area of the transistor Qll n times the emitter junction area of the transistor Q+o, the collector current 111 of the transistor Qll is made n times the collector current IIo of the transistor Q+o.

Furthermore, the emitters of transistors Q 12 and Q 13 are commonly connected to the collector of transistor Q1t, and a differential amplifier (5
) is configured, and the bases of the transistors Q 121 Q 13 are connected to the Q terminal and the Q terminal of the flip-flop (3).

Also, transistor Q14. Q16 constitutes a current mirror circuit (6) with terminal T1 as a reference potential point and transistor Q14 as an input terminal, the collector of transistor Q1+ is connected to the collector of transistor Q12, and the collector of transistor Q15 is connected to transistor QIG. Connected to the collector.

Is this transistor Q1g transistor Q1? Together with the current mirror circuit (7), the terminal T2 is the reference potential point and the transistor Qu is the input side.

In addition, the terminal T1 is connected by the transistors Q1e and Qts.
A current mirror circuit (8) is constructed with Q1s as a reference potential point and transistor Q1s as an input side, the collector of transistor Ql11 is connected to the collector of transistor Q□3, and the collector of transistor Q1s is connected to transistor Ql? , and these collectors are connected to terminal T4.

Further, the collectors of the transistors Q1v and Qts are connected to the non-inverting input terminal of the comparator circuit (11, (2)).

Further, for example, the output terminal T5 is taken out from the Q terminal of the flip-flop (3).

Then, the circuit described above is integrated into one IC, the power supply terminal To is connected to the terminal T1, the terminal T3 is connected through the resistor Ro, the terminal T2 is grounded, and the terminal T4 is connected to the ground. A capacitor Co is connected between them.

According to such a configuration, the power supply voltage Vcc of the terminal To is divided by the elements R1 to R3, Ql, and the comparator circuit (11
, (21 are supplied with predetermined reference voltages Emax and Emin. Also, if the base-emitter voltage of the transistor Q1o is VIO, then 1 +o=(Vcc V+o)/R.

Therefore, the collector current 111 of the transistor Qu is Iu=n11°=n (Vcc-Vso)/Ro-(i>).

Now, if the flip-flop (3) is reset, its Q output is "L" and its Q output is "H", so transistor Q12 is off and transistor Q13 is on, and a solid line is drawn at the collector of transistor Qsv. A current 111 flows as shown in FIG.

The collector current of the transistor Q1i is also the collector current of the transistor Q1e, and since the transistor Q1e+Q10 constitutes a current mirror circuit (8), a current 111 flows through the collector of the transistor Q19 as shown by a solid line.

Further, at this time, since the transistor Q12 is off, the transistor Q14 is also off, so the transistor Q15 is off, and the transistors Q16 and Q17 are also off.

Therefore, when the flip-flop (3) is reset, the current 1 from the collector of transistor Q11 is
1.1 flows through the capacitor Co and charges the capacitor Co, and its terminal voltage Eo is during the period t1 in Fig. 2.
It gradually increases as shown in .

Then, when the voltage Eo increases and becomes Eo=Emax,
The output of the comparison circuit fl) changes from "L" to "H", thereby setting the flip-flop (3). Then, the Q output becomes "H" and the Q output becomes "L", so the transistor Q12 is turned on and the transistor Q13 is turned off, and a current In flows through the collector of the transistor Q12 as shown by the broken line. The collector current of transistor σ12 is the collector current of transistor Q14, and the collector current of transistors Q 14 , Q 16 and Q
1ε and Q17 constitute the current mirror circuits (6) and (7), so the transistor Q1? A current 111 flows through the collector as shown by the broken line.

Also, at this time, since transistor Q13 is off, transistor Q1. is also off, so that transistor Q19 is also off.

Therefore, when the voltage Eo rises to the voltage Emax, the charging of the capacitor Co is stopped and the current is discharged through the transistor Gltt at a rate of 111, so that the terminal voltage Eo becomes as shown in period t2 in FIG. It gradually descends.

Then, when the voltage Eo decreases and becomes Eo=Emin,
The output of the comparison circuit (2) changes from L'' to H'', thereby resetting the flip-flop (3). Therefore, the terminal voltage Eo increases as described above.

In this way, the capacitor Co is repeatedly charged and discharged between the voltages E max and E min, and at this time, since the flip-flop (3) is repeatedly set and reset, a rectangular waveform oscillation output is generated at the terminal T5. is obtained.

At this time, if the voltage between the base and emitter of transistor Q1 is 1, then Emax - Emtn = (R2 + R3) (VC
CVt )/(R1+R2) (11). Then, the oscillation period to is: to = tt + t2 = 2 (Emax - Emin) Co / T
11...(iii) Therefore, by substituting (i>, (ii)) into equation (iii), we obtain...(iv).

And transistor Q1. If the current density of Q+o is equal, ■1°V+.

Therefore, equation (iv) is further becomes.

That is, the oscillation frequency or oscillation period of the oscillation circuit in FIG. 1 is determined by the elements R1 to R3, C
It is determined only by o, Ra, and the current ratio n of the current mirror circuit (4), and is not affected by the power supply voltage Vcc, temperature, etc. Then, in equation (v), (R2+R3) / (
Rt + R4) is a resistance ratio, which, like the current ratio n, allows a sufficient degree of resistance to be obtained in the IC.

Therefore, if the elements Ro and Co are provided externally and are sufficiently accurate and stable, accurate and stable oscillation output can be obtained at the desired oscillation frequency.

Thus, according to the present invention, since the power supply voltage, temperature, etc. are not included in the equation giving the oscillation frequency or oscillation period, it is possible to obtain an oscillation output with a stable frequency with respect to the power supply voltage, temperature, etc. Further, all variables in the equation giving the oscillation frequency or oscillation period can be made more accurate by externally attaching the elements Ro and Co, so that a highly accurate oscillation frequency can be obtained.

Furthermore, since the oscillation frequency or oscillation period is not affected by voltage, there is no need to prepare a constant voltage circuit, which is advantageous for IC implementation. In addition, the terminals required to externally connect the elements Ro and Co are 2 (1!) terminals T-3 and T→, and from this point as well, the merits of IC implementation are not impaired.Moreover, the capacitor C.

Changes in charging/discharging current are smooth and do not generate spike noise.

Note that when this circuit is integrated with other circuits into an IC and the output of the constant voltage circuit can be used, the resistors Ro and R
Instead of the voltage Vcc, the constant voltage output of the constant voltage circuit may be supplied to t, and in that case, R = O.

〔Effect of the invention〕

According to the present invention, since power supply voltage, temperature, etc. are not included in the equation giving the oscillation frequency or oscillation period, it is possible to obtain an oscillation output with a stable frequency with respect to the power supply voltage, temperature, etc. Further, all variables in the equation giving the oscillation frequency or oscillation period can be made more accurate by externally attaching the elements Ro and Co, so that a highly accurate oscillation frequency can be obtained.

Furthermore, since the oscillation frequency or oscillation period is not affected by voltage, there is no need to prepare a constant voltage circuit, which is advantageous for IC implementation. Further, the terminals necessary for externally attaching the elements Ro and Co are terminals T3. It is 2(ll) of T4, and from this point as well, the merits of IC implementation are not lost.Moreover, capacitor C.

Changes in charging/discharging current are smooth and do not generate spike noise.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a connection diagram of an example of the present invention, and FIGS. 2 to 6 are diagrams for explaining the same. (11, (21 is a voltage comparison circuit. Combined 11 circuit j. Figure 3 Figure 4

Claims (1)

[Claims] A DC voltage having a predetermined magnitude is divided by a series circuit of a resistor and a transistor to form first and second reference voltages, and the DC voltage is connected to a resistor that determines the oscillation frequency. , a direct current of a predetermined magnitude is supplied to a series circuit with the transistor on the input side of the first current mirror circuit and taken out from the transistor on the output side of the current mirror circuit, and the capacitor is connected to a capacitor that determines the oscillation frequency. A second current mirror circuit for charging is connected, a third current mirror circuit for discharging the capacitor is connected to the capacitor, and the terminal voltage of the capacitor and the first and second reference voltages are set to a second current mirror circuit. The first and second voltage comparator circuits compare each other, and each comparison output of these first and second voltage comparator circuits is
The output current of the first current mirror circuit is supplied to the set input and reset input of the flip-flop respectively, and the output current of the first current mirror circuit is alternately supplied to the second current mirror circuit and the third current mirror circuit. An unstable multivibrator that extracts oscillation output by supplying it to the