Power amplifier electronic circuits-tube audio rf amplifiers

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

May 13th, 2010

Audio Distortion Meter Circuit

Circuit Description

The circuit diagram of audio distortion meter has been described here. Audio distortion meter is used to measure Total Harmonic Distortion (THD) on any load. This device can measure harmonic distortion at any output power. In this circuit, different load resistors of R1 (2 ohm), R2 (4 ohm), R3 (8 ohm), R4 (16 ohm) is selected by means of a switch S1. This circuit a filter called Notch filter which is composed of resistor R1, capacitors C1 (0.01 uF) and C2 C1 (0.01 uF) and inductor L1.

Feed the input of 1 KHz signal from a signal generator amplifier circuit. Connect the out put of amplifier to points P1 and P2 of the circuit. Then select the required load resistance using switch S1. Slide the switch S2 to CAL position (to left as in circuit) and note the reading on the AC meter (Vcal). Then slide switch S2 to THD position (right) and adjust L1 and R5 (250K) to get the minimum meter reading (Vmin). Calculate THD by using the following equation.

THD (%) = (Vmin / Vcal) *100

Circuit Diagram

Audio Distortion Meter Circuit

Audio Distortion Meter Circuit

Notes

  • Load resistors used here should have a rating at least twice of the power dealing with this circuit.
  • Inductor L1 is a UTC VC 15 variable inductor.
  • Meter M1 should be a general purpose AC voltmeter with range determined by the maximum possible output voltage of the amplifier under test.

May 13th, 2010

Simple Multi-Tone Alarm Circuit

Circuit Description

Figure shows the circuit diagram of multi tone alarm. This is basically an amplifier circuit. The central part of this circuit is the dual operational amplifier IC MC 1458 and the operational amplifier LM 380. The IC MC 1458 consists of two operational amplifiers which are used in this circuit as square and triangular wave generators. The operational amplifier LM 380 is used as the output power amplifier.

Out of the two operational amplifiers in MC 1458, one is connected as astable multivibrator to generate square wave and the other is connected as integrator to generate triangular wave from square wave. One of the two outputs among square and triangular is selected using a switch S1 before giving it into the final amplification stage. The final amplified output is used to drive the speaker. A dual DC power supply of is used here for powering the circuit.

Circuit Diagram

Simple Multi-tone alarm circuit

Simple Multi-tone alarm circuit

Notes

  • Use a good quality PCB to assemble this circuit.
  • This circuit can be used in burglar alarms or sirens.
  • POT R4 is used for tone adjustment.
  • The inverting input (pin 6) of IC LM 380 has no connection.
May 13th, 2010

Simple Lead-Acid Battery Charger Circuit

Circuit Description

The circuit diagram of lead acid battery charger has been described here. The core part of this circuit is the IC LM 317. The function of this IC in this circuit is to provide the correct charging voltage for the battery. One of the most important criteria is followed in the design of this circuit that is the battery must be charged with one tenth of its Ah value.

The operation of this charger circuit is determined mainly by the transistor Q1 (BC 548) and the resistors R1 (0.5 ohm), R4 (100 ohm) and R5 (1K). The current through R1 increases as the battery gets charged. The conduction state of transistor Q1 changes due to this.  The adjust pin of IC 317 is connected to the collector of Q1 so that the output voltage changes accordingly. The circuit reduces charging current when the battery is fully charged this mode is called trickle charging mode.

Circuit Diagram

Lead-Acid Battery Charger Circuit

Lead-Acid Battery Charger Circuit

Notes

  • Use a good quality PCB to assemble this circuit.
  • Adequate heat sink should be provided for IC LM 317.
  • Potentiometer R5 is used to set the charging current.
  • In order to get 12 V for charging the battery, the input to the IC must be minimum 15V.