Power amplifier electronic circuits-tube audio rf amplifiers

Electronic Amplifier Circuits-Power amplifier, audio amplifier designs and circuits

June 2nd, 2010

Capacitance Meter Circuit

Circuit Description

The circuit diagram of simple capacitance meter has been published here. The core part of this circuit is the frequency to voltage converter IC LM 2917 developed by National Semiconductors. This IC LM 2917 is a monolithic IC having a very high gain. This IC has got its primary application in tachometers. It can also be used for other applications as well.

This is a capacitor measurement circuit that displays capacitance by using a meter M1. The capacitor Cx whose capacitance is to be measured is connected between the pin2 of the IC and ground. The capacitance Cx will be proportional to the output voltage of the IC. At the output pin (pin4), a resistor R2 (10K) is connected as load. The voltage across this is displayed through a voltmeter (M1) which is connected across R2.

Circuit Diagram

Capacitance Meter Circuit

Capacitance Meter Circuit

Notes

  • Use a Vero board to assemble this particular circuit.
  • Use a suitable holder to mount the IC LM 2917.
  • Capacitance values from 0.01uF to 0.1uF can be measured using this circuit.
  • Potentiometer R1 (200K) can be used for calibrating this circuit.
  • Use a 10V FSD voltmeter in place of M1.
June 1st, 2010

Light Activated Switch

Circuit Description

The circuit diagram of light activated switch circuit has been described here. The core part of this circuit is the operational amplifier IC LM 311which acts as a voltage comparator here. This circuit also consists of an LDR which senses light intensity. A transistor Q1 (BC 107) is included in this circuit for driving the relay.

The non-inverting terminal of comparator is given with 6 V fixed voltage by using resistors R3 and R4 (10K). The voltage at the inverting terminal is the voltage across LDR which is variable according to the intensity of light falling on it. When light intensity is low (darkness), the resistance of LDR will be high and hence the voltage across it. Then the output of comparator will become low and relay becomes inactive. If light intensity increases, the resistance of LDR decreases. As a result of this comparator output will become high and it turns on relay. So relay switches according to the light intensity and which is the desired output of this circuit.

Circuit Diagram

Light Activated Switch

Light Activated Switch

Notes

  • Use a good quality PCB to assemble this circuit.
  • Adjust potentiometer R1 to set the desired light intensity for switching the relay.
  • Use a 12 V battery or 12V DC regulated power supply for powering this circuit.
  • The chance of oscillation in this circuit can be minimized by shorting the pins 5 and 6 of IC LM 311.

May 31st, 2010

Simple Function Generator Circuit

Circuit Description

Here is the circuit diagram of common function generator circuit. The central part of this circuit is the function generator IC ICL 8038. This function generator IC can generate waveforms such as sine, square and triangular at the same time. This IC has got an added feature that it can control the waveform parameters such as frequency, duty cycle and distortion. The frequency of the output waveform is adjusted using potentiometer R7 (100K). The potentiometer R3 (1K) is used for adjusting the duty cycle of the waveforms. Adjustments in distortion of the waveforms are accomplished by the potentiometer R5 (100K). This circuit is designed to produce waveforms with frequency range between 20Hz and 20 kHz. The function generator IC requires dual DC power supply. A dual power supply of -15/+15 as shown in the circuit is used here for powering this circuit.

Circuit Diagram

Simple Function Generator Circuit

Simple Function Generator Circuit

Notes

  • Use a good quality PCB to assemble this circuit.
  • This is the best function generator circuit for a beginner to start with and is of course a must on the work bench of an electronics hobbyist.
  • Square, triangle and sine waveforms are obtained simultaneously from pins 9, 3, 2 respectively of the function generator IC.