JPS58162116A - Limiter circuit - Google Patents

Abstract

PURPOSE:To form a limiter having an amplifying operation, by inputting the voltage through a diode which is reversely connected to the base of a transistor. CONSTITUTION:A diode 2 is biased to an on-state by a resistance. An input signal is applied to an anode of the diode 2. While anode voltage of the diode 2 does not exceed bias voltage applied to a cathode of the diode 2, the diode 2 is on, but when it exceeds the bias voltage, the diode 2 becomes off. An operating point of a transistor 6 is set so as to be cut off when base voltage becomes below an optional level, therefore, only waveform voltage exceeding its level is amplified and appears in a load 5. Since this limiter has both gain and limiter operations by a simple circuit, it is suitable for a line repeater, etc. whose space is limited.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a limiter circuit used in a self-timing type regenerative repeater of a digital communication system.

Conventionally, there are limit circuits that use only the switching action of diodes and those that use only the cutoff action of transistors. However, the former increases 11
Since it does not have the m function, amplifiers must be connected in cascade and used, and the latter has to pass through a two-stage cutoff circuit, which increases the number of cumulators and increases the circuit regulation. This is not desirable for line repeaters, etc., where mounting area and power consumption are severely limited.

The object of the invention is to improve the above-mentioned drawbacks, and to provide a limiter circuit that performs all amplification functions with a simple circuit configuration.

Describing the structure of the present invention, a load is connected between the collector of a transistor whose emitter is grounded and a positive power supply, two resistors are connected in parallel between the positive power supply and the ground, and the two resistors are connected in parallel between the positive power supply and the ground. A connection point of the resistor is connected to the base of the transistor and an anode of the diode, a resistor is connected between the cathode of the diode and ground, and the cathode of the diode is connected to the input terminal,
Further, the collector of the transistor is a limiter circuit connected to an output terminal.

The present invention will be explained below by way of examples and with reference to the drawings.

FIG. 1 shows a circuit diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing waveforms at each point in FIG.

In FIG. 1, diode 2 is forward biased by a positive power supply via resistor 1 and resistor 3, so it is always on when there is no input signal.

Next, let the voltage at point a connected to the input terminal be v&, and the voltage at point b connected to the anode of diode 2 be vb.

First, when an input voltage having a waveform as shown by a solid line or a broken line in FIG. 2a becomes an input signal, va changes in the same way as the input signal waveform.

At this time, the diode 2 is in the ON state in the time range where %vEL<vb, and the diode 2 is in the OFF state in the time range where va≧vb. The input signal is.

When the diode 2 is on, the forward voltage drop of the diode 20 is clamped and appears at point b, and the voltage waveform at point b becomes as shown in FIG. Next, the voltage waveform at point b becomes the input 3- signal of transistor 6. Here, the operating point of transistor 6 is:

Resistors 3 and 4 are set so that the cutoff occurs when the voltage waveform at point 6b falls below a certain level.
Only waveform voltages above that level are amplified and appear on the load 5. Therefore, the tIE waveform at point 0 is as shown in FIG. 2C.

As explained above, according to the present invention, a limiter circuit having an amplification effect can be constructed with a simple circuit due to the amplification and cutoff effect of the transistor 6 and the switching effect of the diode 2, so that it can be implemented as a single circuit. A limit circuit can be obtained that is extremely suitable for line repeaters, etc., which have severe restrictions on area, power consumption, etc.

[Brief explanation of drawings]

FIG. 1 shows a circuit diagram of an embodiment of the present invention, and FIG. 2 shows voltage waveforms at points a, b, and 0 in FIG. Note that the symbols used in the drawings indicate the following.

Claims (1)

[Claims] A load is connected between the collector of the transistor whose emitter is grounded and a positive power supply, two resistors are connected in series between the positive power supply and the ground, and a connection point of the two resistors is connected to the base of the transistor. and is connected to the anode of the diode, a resistor is connected between the cathode of the diode and ground, the cathode of the diode is connected to the input terminal, and the collector of the transistor is connected to the output terminal. The limit, the circuit.