JPH0265511A - Emitter grounded amplifier - Google Patents

Abstract

PURPOSE:To obtain an excellent output characteristic to an input of a burst signal by supplying a base bias voltage to the base of a transistor(TR), supplying a collector bias voltage to the collector and extracting an output signal from the collector. CONSTITUTION:A collector of an NPN TR is connected to a collector bias voltage Vcc via a collector resistor Rc and an output signal Vout is extracted from the collector. The base is connected to the Vcc via a base resistor RB and receives an input signal Vin. Then the emitter is connected to ground via a parallel circuit comprising a Zener diode Dz and a capacitor CE, A voltage across the diode Dz does not rise over the Zener breakdown voltage. Thus, even if a burst signal is inputted to the base, the emitter potential does not almost change and the output signal Vout is shown in figure (c) and the same potential of inputs is nearly of the same potential at outputs.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electronic circuits, and more specifically to a common emitter amplifier suitable for amplifying burst signals.

Prior Art FIG. 4 is a circuit diagram of a typical conventional common emitter amplifier. The illustrated emitter-grounded amplifier is equipped with an NPN) transistor Tr, and has a base resistor RB.
A base bias voltage vBB is supplied via the input signal V1, and an input signal V1 is applied thereto. A collector bias voltage VCC is supplied to the collector via a collector resistor Rc, and an output signal V is supplied from the collector. ut is taken out.

Then, the emitter is connected to the emitter resistor R2 and the capacitor C.
It is grounded through a parallel circuit with 8.

Problems to be Solved by the Invention When a burst signal consisting of pulses from a reference potential only in the positive direction, as shown in Fig. 5(a), is input to the base of the conventional common emitter amplifier shown in Fig. 4, , since the emitter potential changes as shown in FIG. 5(5), the collector output becomes as shown in FIG. 5(C). Therefore, there is a problem that the input signal has the same potential but the output signal has a different potential. This results in constraints on conditions for subsequent signal processing such as comparison with a threshold value, which is undesirable.

In the common emitter amplifier shown in Fig. 4, the reason why the emitter potential rises when a burst signal is input manually is as follows.
Emitter resistance RI! This is thought to be due to the time constant of the capacitor C2 and the emitter capacitor C2, so that the charge of the capacitor C5 is not sufficiently discharged during the low level period between each pulse of the burst signal to maintain the emitter potential.

Therefore, the present invention solves the above-mentioned problem and provides a common emitter amplifier in which the reference potential of the output signal when receiving a burst signal is substantially the same as the reference potential of the output signal when no signal is received. That is.

Means for Solving the Problems The common emitter amplifier according to the present invention has one transistor Tr, as shown in FIG.
The base of r is supplied with the base bias voltage VBB (via the base resistor R6) and the input signal V I
n is applied, and a collector bias voltage V is applied to the collector (via collector resistor R6). C is supplied and output signal V from its collector. uL is taken out, and the emitter is connected to the emitter bias voltage V through a parallel circuit of Zener diode Dz and capacitor C6.
.

It is connected to the.

Operation In the common emitter amplifier according to the present invention configured as described above, even if a burst signal as shown in FIG. As shown in Figure 2, etc.), there is almost no change. That is, the voltage does not rise above the Zener breakdown voltage of the Zener diode. Therefore, the collector output becomes as shown in FIG. 2(C), and even if the outputs are at the same potential manually, they will be at almost the same potential.

Embodiment FIG. 3 shows an embodiment of a common emitter amplifier according to the present invention. The collector of the N P N ) transistor Tr is connected to the collector bias voltage VCC via the collector resistor Re, and the output signal V05. is taken out. The base also has a collector bias voltage V via the base resistor R8. 0 and input signal V l
n is applied. The emitter is grounded via a parallel circuit of a Zener diode Dz and a capacitor C6.

The voltage across the Zener diode Dz does not rise above its Zener breakdown voltage. Therefore, the transistor T
The emitter potential of r does not rise above the ground potential beyond the Zener breakdown potential of the Zener diode Dz. Therefore, even if a burst signal is input to the base, the emitter potential hardly changes and the output signal V. uL is as shown in Figure 2 (C)
It becomes as follows, and the parts that have the same potential by human power will have almost the same potential in the output.

As described in detail, the common emitter amplifier according to the present invention has good output characteristics against burst signal input, so it is effective when used in digital signal circuits and optical communication receiving circuits. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic configuration of the common emitter amplifier according to the present invention. FIG. 2 is a waveform diagram explaining the operation of the common emitter amplifier according to the present invention shown in FIG. 1. FIG. 4 is a circuit diagram showing an example of a conventional common emitter amplifier, and FIG. 5 is a waveform explaining the operation of the conventional common emitter amplifier shown in FIG. 4. It is a diagram. (Main reference numbers) Tr...Transistor, VBB, VCC, VEE...Bias voltage, RaCE, D2, V3. ,・ Vou L Rc , RE ・・Resistor, ・Capacitor, ・Zener diode, ・Input signal, ・・Output signal

Claims (1)

[Claims] It has one transistor, the base of the transistor is supplied with a base bias voltage and an input signal is applied, the collector is supplied with a collector bias voltage, an output is taken out from the collector, and an emitter A common emitter amplifier characterized in that it is connected to the emitter bias voltage through a parallel circuit with a Zener diode and a capacitor.