JPH05235676A - Limiter circuit - Google Patents

Abstract

PURPOSE:To change limiter voltage width and to form a circuit adaptive for making into an IC by setting a reference voltage with respect to a source volt age with a desired ratio, and cutting by deviating an input signal with amplitude setting the reference voltage as reference in a positive or negative direction. CONSTITUTION:The input signal Vin(a) is biased(signal (b)) so as to perform amplitude setting the potential of the reference voltage Vcc/2 as reference by R5, R6. The signal (b) is level-shifted by Vbe of a Q1 and I1XR1 by the Q1 and the R1, and its negative side is clipped(signal (c)) by the GHD potential. The signal (c) is leveled up by Vbe of a Q2 and I2XR2 by the Q2, the R2, and a Q3, an R3, and furthermore, it is biased by Vbe of the Q3 and I2XR3, and its positive side is clipped(signal (d)). Furthermore, the signal (d) is level- shifted by Vbe of a Q4 and I3XR4 by the Q4 and the R4, then, the DC bias value of the signal in which both positive and negative sides are clipped is taken out by setting at a desired value.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a limiter circuit,
In particular, it relates to improvement of the control system of the limiter voltage width.

[0002]

2. Description of the Related Art A conventional limiter circuit is shown in FIG. 9 and its input waveform is shown in FIG. The conventional limiter circuit is composed of diodes D1 and D2 and bias voltage sources E1 and E2, and the respective limiter voltages VL1 and V2.
L2 is the voltage of E1 and E2 and the forward voltage VD of the diode
1, based on VD2, formula; VL1 = E1 + VD1, formula VL
It was set to the value obtained by 2 = E2 + VD2. Further, in the conventional limiter circuit, a power source having a sufficiently low impedance has to be used as a voltage source for determining the limiter voltage.

[0003]

For this reason, there has been a drawback that power consumption is increased in the IC circuit of the limiter circuit. Further, there is a problem that the limiter characteristic (which means a limit value of upper and lower levels, the same applies hereinafter) is a fixed value determined by the power supply voltage and the forward voltage of the diode, and cannot be made variable. It is an object of the present invention to provide a limiter circuit that can change the limiter voltage width by a control signal, consumes less power, and is suitable for use as an IC.

[0004]

In order to achieve the above object, a limiter circuit according to the present invention uses a voltage setting circuit for setting a reference voltage at a desired ratio with respect to a power supply voltage and a potential of the reference voltage as a reference value. The amplitude of the input signal is deviated to either positive or negative direction.If the deviation direction is negative, the negative side of the input waveform is sheared by the potential of the ground voltage. A first shift circuit that shears the side by the potential of the power supply current, and an input signal that has passed through the first shift circuit,
The first shift circuit shifts in the direction opposite to the shift direction. When the shift direction is positive, the positive side of the input waveform is sheared by the potential of the power supply voltage, and when it is negative, the negative side of the input waveform is changed. The present invention is characterized by including a second shift circuit that performs shearing according to the potential of the ground voltage, and a setting circuit that sets the DC bias value of the signal shifted by the second shift circuit to a desired value.

[0005]

The input signal is biased by the voltage setting circuit so as to oscillate with reference to the potential of the reference voltage. The biased input signal is level-shifted by a potential determined by the potential of the reference voltage. When the shift direction is negative, the negative side of the input waveform is clipped by the ground potential.
The clipped signal on the negative side of the waveform is leveled up by a predetermined potential in the opposite direction, and after being further biased, the positive side of the input waveform is shifted by the potential of the reference voltage. The potential increase in this case is the compensation potential of the first-stage level shift value by the first shift circuit, and the clipping potential on the positive side of the input waveform is determined by this. In addition, the signal clipped on the positive side of the waveform has a higher bias potential by the level increase value of the second stage, so the level is shifted by the setting circuit that corrects and sets the DC value, and the signal clipped on both the positive and negative sides. The DC bias value of is set to a desired value and is taken out. Even when the initial shift direction is positive, the order of shearing of the input waveform is switched, and the level is raised by the setting circuit, and the same as above.

[0006]

1 is a block diagram showing the configuration of a limiter circuit according to the present invention. The limiter circuit 1 shown in FIG.
As shown in FIG. 5, an input bias circuit 11 forming a voltage setting circuit for setting a reference voltage having a desired ratio with respect to the power supply voltage Vcc, and a level shift circuit forming a first shift circuit for shifting a signal to the negative side. 12 and a level-up circuit 13 forming a second shift circuit for shifting the signal to the positive side.
And a level shift circuit 14 as a setting circuit for correcting the output DC bias value and setting it to a desired value. In the limiter circuit of the present invention, the order of the level shift circuit and the level up circuit is exchanged, and the level up circuit 12 as the first shift circuit for shifting the output signal of the input bias circuit 11 to the positive side as shown in FIG. 1B. 'And a level shift circuit 13' as a second shift circuit for shifting the signal to the negative side, and a level up circuit 14 'as a setting circuit for correcting the output DC bias value and setting it to a desired value. Yes (see Example 2 below).

FIG. 2 is an equivalent circuit of the limiter circuit 1 shown in FIG. 1A. The circuit shown in FIG. 2 has a power supply voltage Vcc
An input bias circuit 11 that sets a reference voltage having a desired ratio determined by R5 and R6, a level shift circuit 12 that uses Q1, R1, and I1 to shift (shift) the signal to the negative side, and a signal to the positive side. Q2, R2, I2 to shift
2 and a level shift circuit 14 for compensating the output bias composed of Q4, R4 and I3. (A) to (e) are signals of the respective constituent parts and are shown in FIG.
Shows the waveform.

The input signal Vin (a) is biased by the input bias circuit 11 composed of R5 and R6 so as to swing with reference to the potential of the reference voltage Vcc / 2 (signal (b)). The signal (b) Q1 and R1 level-shifts the Vbe of Q1 and the potential of I1 × R1 by the potential of the reference voltage Vcc / 2, and the negative side of the input waveform is clipped (sheared) by the GND (ground) potential. c)). The signal (c) with the negative side of the waveform clipped is raised by V2 of Q2 and the potential of I2 × R2 by Q2, R2, Q3 and R3, and further biased by the potential of Vbe of Q3 and the potential of I2 × R3. The positive side of is clipped by the Vcc potential (signal (d)). In this case, the increase in Vbe of Q3 and the potential of I2 × R2 is the compensation potential of the first-stage level shift value by Q1 and Q2, whereby the clip potential on the positive side of the input waveform is Vbe of I2 and I2 × R3. It will be decided by the potential of.
Further, since the bias potential of the signal (d) with the positive side of the waveform clipped is higher by the level increase value of the second stage, Q4 and Q4 formed by Q4 and R4 forming the setting circuit 14 that corrects and sets the DC value. Vbe and the potential of I3 × R4 are level-shifted, and the DC bias value of the clipped signal on both the positive and negative sides is set to a desired value and taken out (signal (e)). As a result, Vbe of the transistors Q2 and Q4 is
Are equal, the resistance values of R2 and R4 are the same, and I2 and I4
By setting the current values of 3 to be the same, the output bias potential of the limiter circuit 1 is Vcc / 2 set by R5 and R6.
Becomes equal to the input bias potential of. The above-described relations of the limiter potentials are as shown in the following formula 1, formula 2, and formula 3. That is, the positive limiter potential VL1 is

[0009]

[Equation 1] The negative limiter potential VL2 is

[Equation 2] Furthermore, the output bias potential Vout is

[Equation 3] If the Vbe voltage of Q1 to Q4 and the resistance value of R1 to R4 are equal, and the current values of I1 to I3 track (follow) and supply the same current value, then Equation 3 is become that way.

[Equation 4]

<First Embodiment> FIG. 4 shows an embodiment of a limiter circuit according to the present invention. In FIG. 4, R1
Reference numerals 2 and 13 denote input bias circuits 11 for fixing the input signal. The constant current circuit composed of Q1, R1 and Q6 to Q9, R6 to R8 constitutes a level shift circuit 12 for clipping the negative side of the input signal, and Q2, R2 and Q2.
The constant current circuit composed of 3, R3 and Q11 to Q13, R10, R11 constitutes a level-up circuit 13 for performing positive side clipping. The bias values of Q3 and R3 are configured to be equal to the level shift values of Q1 and R1.

Further, Q4, R4 and Q6, Q7 and Q10,
The constant current circuit composed of R6 and R9 is the setting circuit 1
4 and the signal whose positive and negative sides are clipped is Q2 and R2.
The level is shifted by the same amount as the level-up value of and output. In this circuit, the constant current circuit composed of Q6 to Q13 and R5 to R11 tracks the control voltage Vc and supplies the same current value. The control current is set by the control voltage Vc and Q5 and R5. The relationship between the control voltage Vc and the set current I is as shown in the following mathematical formula 5.

[0012]

[Equation 5]

Therefore, by using complementary transistors having the same Vbe voltage for Q2 and Q4 and providing resistors of the same resistance value to R1 to R4, the control voltage Vc
It is possible to obtain a limiter circuit in which the limiter voltage width changes in a positive / negative contrast manner in proportion to the voltage. In FIG. 4, the control voltage Vc is shown as a current voltage having a fixed value,
An arbitrary control voltage Vc can be set using a variable resistor and a power supply. The limiter voltage width VLW in this case takes the value of the following formula 6.

[0014]

[Equation 6]

The resistance ratio of R1 to R4 or Q6 to
By changing the level shift amount by changing the current ratio of the constant current source consisting of Q12 and R6 to R11, the limiter position is changed as shown in FIG. The characteristic VR can be set. Similarly, in the present invention, the input signals are input to R12 and R13.
Although it is set to the potential of Vcc / 2 by the bias resistance of, the bias value must be changed, that is, R12 and R
By changing the ratio of the resistance value with 13, the positive or negative limiter voltage can be set asymmetric as shown in FIG. 6B. In other words, for example, it is possible to change the GND potential with the waveform as shown in FIG. 6B. This means that even if | VU | = | VL | in FIG. 6A, the limiter voltage control characteristic is as shown in FIG. 6B. Means that can be set. Further, as shown in FIG. 7, the above operation can be easily realized by using R1 and R6 as variable resistors. Furthermore,
Other resistors can be appropriately used as variable resistors to make the limiter voltage width and the like variable and set arbitrarily. Furthermore, although the control voltage Vc is used to control the limiter voltage in the present embodiment, it goes without saying that the limiter voltage can be similarly controlled by directly controlling the reference current of the constant current source.

<Embodiment 2> FIG. 8 shows another embodiment of the limiter circuit according to the present invention. The present embodiment is a modification of the above-described first embodiment, in which R12 and R13 are bias circuits 11 for fixing an input signal, and Q1, R1 and Q1.
The constant current circuit 11-Q13, R10, R11 constitutes a level-up circuit 12 'for clipping the positive side of the input signal, and Q2, R2 and Q3, R3 and Q6-Q.
The constant current circuit composed of 9, R6 to R8 constitutes a level shift circuit and a bias circuit 13 'for performing the negative side clipping. The bias values of Q3 and R3 are Q1 and R
It is configured to be equal to the level up value of 1. The signals clipped on the positive and negative sides are Q4, R4 and Q10, Q11,
A setting circuit 14 'formed by a constant current circuit composed of Q13 and R9, R10 raises the level by the same level as the level shift value of Q2, R2, and outputs the combined input and output levels. Also in this embodiment, the upper and lower non-contrast limiter voltage control characteristics can be set and the positive or negative limiter voltage can be set to the non-contrast in the same manner as in the first embodiment, the limiter voltage width, etc. Can be made variable and can be set arbitrarily, and the limiter voltage can be controlled by directly controlling the reference current of the constant current source.

[0017]

As described above, according to the limiter circuit of the present invention, the positive or negative limiter potential can be simultaneously changed by following the control signal by the voltage or the current. Further, the balance of the positive and negative limiter characteristics can be set arbitrarily. Furthermore, since the limiter circuit of the present invention does not require a voltage source that requires low impedance, it is possible to reduce the power consumption of the circuit and is suitable for an IC.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a limiter circuit according to the present invention.

FIG. 2 is an equivalent circuit of a limiter circuit according to the present invention.

FIG. 3 is a waveform diagram of each component of the equivalent circuit shown in FIG.

FIG. 4 is a circuit diagram of an embodiment of a limiter circuit according to the present invention.

FIG. 5 is an explanatory diagram of a setting example of a limiter voltage control characteristic that is not symmetrical between upper and lower sides.

FIG. 6 is an explanatory diagram of a setting example of a limiter voltage set as a non-contrast.

FIG. 7 is a circuit diagram showing a modification of the circuit of FIG.

FIG. 8 is a circuit diagram of another embodiment of the limiter circuit according to the present invention.

FIG. 9 is a circuit diagram of a conventional limiter circuit.

FIG. 10 is an input waveform diagram of the circuit of FIG.

[Explanation of symbols]

 1 limiter circuit 11 input bias circuit (voltage setting circuit) 12 level shift circuit (first shift circuit) 12 'level up circuit (first shift circuit) 13 level up circuit (second shift circuit) 13' level shift circuit (first 2 shift circuit) 14 setting circuit Vcc power supply voltage

Claims (1)

[Claims] 1. A voltage setting circuit for setting a reference voltage at a desired ratio with respect to a power supply voltage, and an input signal oscillating with a potential of the reference voltage as a reference value, which is shifted in one of positive and negative directions. A first shift circuit that shears the negative side of the input waveform by the potential of the ground voltage when the shift direction is negative, and shears the positive side of the input waveform by the potential of the power supply voltage when the shift direction is positive; The input signal that has passed through the first shift circuit is shifted in a direction opposite to the shift direction of the first shift circuit, and when the shift direction is positive, the positive side of the input waveform is sheared by the potential of the power supply voltage, A second shift circuit that, when negative, shears the negative side of the input waveform with the potential of the ground voltage; and a setting circuit that sets the DC bias value of the signal that is shifted by the second shift circuit to a desired value. A limiter circuit having: