JPS59108409A - Amplifier - Google Patents

Abstract

PURPOSE:To display the saturating state of an amplifier by providing a diode and a transistor (TR) for detecting the saturated state between a base and a collector of the TR at the 2nd stage of a multi-stage amplifier circuit and lighting a light emitting diode with this output. CONSTITUTION:When TRs 7, 8 being an output stage are saturated, a signal fed back from negative feedback circuits 9-12 to a TR3 becomes a clip signal and a differential input of TRs 2, 3 is increased. Further, the differential output is increased, a TR4 is over-driven and saturated, its collector potential is lower than the base potential and a diode 18 and a TR19 for detecting the saturated state are turned on. As a result, a current flows to a resistor 20, and a potential difference across the resistor 20 operates TRs 21, 25 so as to light a light emitting diode 26. Since the saturation of the amplifier is known through the lighting, the input level is set easily.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an amplifier for audio signals, etc.

Conventional configuration and its problems First, FIG. 1 shows the circuit configuration of a conventional amplifier. 1 is an input terminal, 2 and 3 are transistors that make up the input differential amplifier 2-2-line film, 4 is a transistor that makes up the entire voltage amplification stage, and 5, 6, and 7.8 are transistors that make up the output stage. 9, 10, 11゜12 is a resistor and capacitor that constitute a negative feedback circuit, 13 is a positive power supply terminal, 14
is an output terminal, and 15 is a negative power supply terminal.

In the conventional amplifier configured as described above, when a signal higher than a specified level is input, the output stage is saturated by the power supply voltage, and a clipped signal appears at the output terminal A14. Therefore, for signals with large level fluctuations such as music signals, it is necessary to set the entire input signal level in advance so that the peak value of this music signal does not exceed the specified input. When amplifying the power of this music signal, as mentioned above, the input must be set so that the amplifier does not saturate even at the peak value of this music signal, and when amplifying at an average level, the power efficiency is extremely poor. .

Purpose of the Invention The present invention provides a new page 3 for a circuit that can detect the saturation state of an amplifier, uses the signal of this detection circuit to display when the amplifier is in the saturation state, and informs input adjustment. It was designed to help.

Structure of the Invention The present invention is an amplifier including an input differential amplification stage, a voltage amplification stage, an output stage, a negative feedback circuit, and a detection circuit for detecting a saturation state, and a display circuit is activated by a signal from the saturation state detection circuit. It was made to work.

DESCRIPTION OF THE EMBODIMENT FIG. 2 shows the circuit configuration of an amplifier in an embodiment of the present invention. In FIG. 2, 1 to 16 are the same as in the conventional example, 16, 17, 18, 19, 20 are diodes, transistors, and resistors that constitute the saturation state detection circuit, and 21, 22, 23, 24, 25 .26 and 27 are transistors, resistors, capacitors, and light emitting diodes that constitute the saturation state display circuit.

The operation will be explained below.

The difference between the signal input to the input terminal 1 and the signal from the output terminal A 14 via the negative feedback circuits 9 to 12 is amplified by the transistors 2 and 3 of the differential amplification stage, and the signal is then applied to the voltage of the next stage. It is amplified by transistor 4 in the amplification stage. transistor 4
The signal amplified by □ is power amplified by the transistors 6 to 8 in the output stage, and is output to the output terminal 14. Here, although the collector potential of the transistor 4 does not normally become lower than the base potential, a large negative input signal exceeding a specified level is applied to the input terminal 1, and the transistor 7, which is a negative output stage, is applied to the input terminal 1.
．． 8 is saturated, the signal fed back from the negative feedback circuit to transistor 3 becomes a clipped signal, the differential input input to transistors 2 and 3 increases, and transistor 4
is overdriven, and its collector potential is lower than its base potential.

The saturated state detection circuits 16 to 20 are capable of detecting a saturated state by utilizing this phenomenon. That is, when the transistor 4 is overdriven and the collector potential of the transistor 4 becomes lower than the base potential, the diode 18.1-transistor 19 of the saturation state detection circuit turns on, and a current of 5p2 flows through the resistor 2o. A potential difference occurs between both ends. Due to the potential difference generated across the resistor 20, the transistor 21 is turned on, and the transistor 25 is also turned on, causing the light emitting diode 26 to light up. The diode 18 is inserted to prevent the pn junction between the emitter and base of the transistor 19 from breaking down when the collector potential of the transistor 4 is sufficiently higher than the base potential. diode 1
6.17 is added to generate a voltage that compensates for the forward voltage v1 of the diode 18 and VBI+ of the transistor 19.

As described above, by knowing from the lighting of the light emitting diode 26 that the amplifier has become saturated due to excessive input, the input level can be easily set.

Effects of the Invention As described above, the present invention can notify the saturation state of the amplification 2g with a simple configuration of adding a saturation state detection circuit and a display circuit, and can adjust the input level to set it to an appropriate level. It can be done and the effect is great.

6 pages

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1...Input terminal, 2, 3, 4, 6. s, 7. B. 19.21', 25...transistor, 26...
...Light emitting diode.

Claims (1)

[Claims] When a multistage amplifier circuit having two or more amplifier circuits, a negative feedback circuit applied to two or more amplifier circuits including an output amplification stage of the multistage amplifier circuit, and the multistage amplifier circuit are saturated due to excessive input, All features include a saturation state detection circuit that detects the saturation state by utilizing a phenomenon in which the multi-stage amplifier circuit is further overdriven by a negative feedback effect, and a display circuit that operates based on the output of the saturation state detection circuit. amplifier.