JPH057115A - Noise eliminating type pulse amplifier circuit - Google Patents

Abstract

PURPOSE:To obtain a noise eliminating type pulse amplifier circuit whose temperature characteristic is stable. CONSTITUTION:The ratio of en emitter resistance R5 of a transistor(TR) Q2 to the base set to a constant voltage for which a pulse signal including noise is inputted to a collector resistance R6 is selected to be R6>>R5. A prescribed voltage set between the pulse signal and the peak of the noise component is applied to the emitter of the TR Q2 from a constant voltage power supply 4 via an element including a PN junction. Since the temperature drift of a VBE of the TR Q2 is canceled by the temperature drift of the element including the PN junction, the influence of a temperature drift is canceled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise elimination type pulse amplifier circuit.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a conventional noise elimination type pulse amplifier circuit, in which 1 is an input terminal, C1 is an input capacitor, R1 and R2 are voltage dividing resistors, Q1 is a transistor and R3.
Is the emitter resistance of Q1 and 2 is the L composed of R4 and C2
PF and Q2 are output transistors, R5 is an emitter resistance of Q2, R6 is a collector resistance of Q2, and 3 is an output terminal.

Next, the operation will be described. A pulse signal a (shown in FIG. 5 (a)) input from the input terminal 1 is input to the LPF2 via Q2 forming an emitter follower amplifier, and a signal b in which the peak level of the noise component n is suppressed.
(Shown in FIG. 5B) is input to Q2. The emitter potential V _{E of} Q2 is determined by R5 and R6, and this emitter potential V _E is a noise component n as shown in FIG.
When it is higher and lower than the pulse signal p, FIG.
As shown in (c), C indicating "H" level is output,
The noise component n is removed. On the other hand, when the level of the pulse signal p is lower than V _E , the output signal C becomes "L" level.

[0004]

In the conventional noise elimination type pulse amplification circuit, when the level difference between the noise component n of the input signal and the pulse signal p is small, Q2 accompanying a temperature change is generated.
Change in V _BE appears as a change in the emitter potential V _E that separates the noise component n and the pulse signal p, and the noise removal effect becomes unstable.

The present invention has been made to solve the above problems, and an object thereof is to obtain a noise separation type pulse amplifier circuit having good temperature characteristics.

[0006]

In the noise elimination type pulse amplifier circuit according to the present invention, the output of the transistor for separating the noise component n and the pulse signal p is compensated so as to cancel the temperature drift of the transistor. It is characterized in that a constant voltage power supply for applying a voltage is provided.

[0007]

In the noise elimination type pulse amplifier circuit according to the present invention, the output voltage from the temperature-compensated constant voltage power source is applied to the transistor which separates the noise component n and the pulse signal p as the emitter potential, so that the temperature change Even if there is, it is possible to cancel the temperature drift of V _BE of the transistor and perform a stable noise removal operation.

[0008]

EXAMPLES Example 1. FIG. 1 is a circuit diagram of an embodiment of the present invention, and the same reference numerals as those in FIG. 4 denote the same or corresponding portions. In the figure, 4 is a constant voltage power source, D1 is a diode, and the output voltage E of the constant voltage power source 4 is applied to the emitter of Q2 via D1.

FIG. 2 (a) is a waveform diagram of the input signal a for explaining the operation of Q2, and FIG. 2 (b) is a waveform diagram of the output signal c of Q2. In the figure, the input signal a from which the DC component is removed by C1 is the base potential V _B by R1 and R2.
Is input to the base of Q2 that has been set. Now, the V _B is 0.5V, the peak level of 0.1V of the noise component n of the input signal a, the level of the pulse signal p 0.45 V
Then, the base potential V _{B of} Q2 is 0.6 V for a noise component and 0.95 V for a pulse signal.

The emitter potential V _{E of} Q2 is the constant voltage power source 4
2 becomes lower than the output voltage E of V1 by the potential drop V _{D1 of D1} , and this potential is set to an intermediate level between the noise component n and the pulse signal p, as shown in FIG.

V _{BE of} Q2 and V D1 of _D1 are almost equal to each other, and the temperature drifts of V _BE and V _D1 are both 2 mV /
Since decrease in the ratio of the degree of ° C, even if the temperature of Q2 changes _{(V B -V BE) - (} E-V D1) ≒ V B -E , and the influence of temperature drift is eliminated. As a result, as shown in FIG. 2C, the output signal c is taken out as a signal of opposite polarity in which only the portion of the pulse signal p that exceeds E-V _D1 is amplified.

The gain of Q2 can be increased by setting R5 >> R6, and by reducing the value of R5, the negative peak value v of the output signal c (see FIG. 2 (c ) Reference) can be made smaller.

FIG. 3 is a circuit diagram of another embodiment of the present invention, in which a constant voltage power source 4 is connected to a transistor Q3 and a resistor R.
7 and R8, which is an emitter follower circuit.

According to this embodiment, the constant voltage power source 4 includes:
V _{BE of} Q3 exists, and output voltage E against temperature drift
Is compensated, the same effect as the embodiment of FIG. 1 can be obtained.

In the above embodiment, NP is used for Q2 and Q3.
Although an N-type transistor is used, a PNP-type transistor can be used in the same manner.

[0016]

As described above, according to the present invention, the output voltage of the constant voltage power source configured to compensate the temperature drift of V _BE of the transistor is applied to the emitter of the transistor for amplifying the input signal. However, since the emitter potential is set between the noise component contained in the input signal and the pulse signal, there is an effect that a noise elimination type pulse amplification circuit free from the influence of temperature drift can be obtained.

[Brief description of drawings]

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

FIG. 2 is a signal waveform diagram for explaining the operation of this embodiment.

FIG. 3 is a circuit diagram of another embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional noise removal type pulse amplifier circuit.

FIG. 5 is a signal waveform diagram for explaining the operation of the conventional example.

[Explanation of symbols]

 4 Constant voltage power supply Q2 Transistor D1 Diode R1, R2, R5, R6 Resistance

Claims (1)

1. A base potential is held at a constant potential by a voltage dividing resistor, and a collector resistor R6 and an emitter resistor R5 are R.
6 >> R5, and a constant voltage power supply for applying a temperature-compensated output voltage to the collector of the transistor so as to compensate the temperature drift of V _BE of the transistor. A noise elimination type pulse amplification circuit characterized by the above.