Transistor Radio Output Stages

Posted on Feb 5, 2014

The driver stage works in the same manner as the class A output stage described previously. However it is only working at a couple of milliamps, so efficiency is not an issue here. The biasing arrangement should be familiar by now. Some sets, including the circuit above, have an extra stage of amplification between the volume control and the drive

Click here to download the full size of the above Circuit.

r stage. Such sets will be able to receive weaker stations better and probably produce higher volume or better quality on stronger signals. This would take the total to seven transistors, whereas sets without this stage have six transistors. These are the standard line-ups, and most early MW/LW sets will have either six or seven transistors depending on the model and original selling price. Because the class AB output stage current consumption varies with the signal being amplified, the current drawn from the supply (battery) varies in sympathy. This will cause the supply voltage to fluctuate. We need to prevent these rapid fluctuations from finding their way back to the driver and earlier stages, otherwise they could cause distortion and/or instability. In the circuit above we have a 100uF capacitor (C7) directly across the power supply. This would be mounted close to the output stage and would smooth the fluctuations. The supply to the driver stage biasing and earlier stages in the set is further filtered or decoupled by a 1k-ohm resistor (R13) and another 100uF capacitor (C5). If this capacitor fails the set will probably make a horrible noise known as "motor-boating" because it resembles the sound of an outboard motor. If the 100uF capacitor directly across the power supply were to fail the same effect would probably occur but only as the battery starts to run down. The main problem with the two-transformer circuit...

Visit page

Leave Comment

characters left:

Related Circuits

2000 Chevrolet Chevy Blazer Wiring Diagram

The Part of 2000 Chevrolet Chevy Blazer Wiring Diagram: power distribution schematic, fuel pump relay control, fuel pump and sender, splice pack, fuel pump prime connector, ground distribution...

Controlling a Mazda Car Using an iPhone

This hack illustrates how a car can be controlled from anywhere in the world by tapping into the disgnostic systems and onboard webserver of the car. The objective is to keep the car live and...

Low Frequency Sine wave Generators Schematic

The two circuits below illustrate generating low frequency sine waves by shifting the phase of the signal through an RC network so that oscillation occurs where the total phase shift is 360...

Simple Indicator for Dynamic Limiter Schematic Diagram

The indicator described here is specifically designed for adjusting the dynamic limiter described elsewhere in this edition and checking whether the maximum level of the reference voltage (P1)...

a d converter

This is the first draft of the pH to 1-Wire converter schematic, and some of the component values are still missing. The original circuit runs on 12 VDC, but since the A/D converter IC must be...

NSLU2

Aquaponics systems need a good water quality, and one of the parameters is pH value, which needs to be within a certain range in order for the fish and plants to thrive. This is of course also true...

Thermal Watt Converter Test Circuit Schematic

AC Wiring Diagram

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

UPS Power Supply

This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5...

12-Bit dac with variable step size

The step size of the converter is variable by selection of the high order data bits. The first...

12VDC to 220VAC Inverter with Sine Wave Output

Here the 50W inverter circuit build based power MOSFET FQB45N03 and IC TL494. This inverter will...

Solar power related schematics

Current meter used to measure the current from a solar panel. It has very low power loss for...

250mW audio amplifier

Here is a very simple three transistor audio amplifier circuit that can deliver 250mW to a 8Ohm...

2002 Chevy Cavalier heater/AC temp control wont light up at nite

The schematic shows these a regular light bulbs, so there is the chance that the bulbs are burned...

ultrasonic transmitter

This section gives step-by-step instructions along with photos to the construction of Ultrasonic...