Basic Audio Amplifier


Posted on Feb 6, 2014

You can clearly see the three stages found in many audio amps (and op amps today). However, looking at actual audio designs, you`ll find the basic topology has been tweaked and enhanced in a few key locations. Here`s a quick tour of design improvements of the audio amplifier. There`s an enhancement for each of the three stages: Differential, Voltage Gain, Output Buffer. Why bother messing with


Basic Audio Amplifier
Click here to download the full size of the above Circuit.

the design Higher gain and better output drive lead to a lower distortion performance. Click on the links below to find out more. The Current Mirror (Q8, Q9) doubles the gain of your differential amplifier. It also balances the current in each transistor (Q1, Q2) nicely. Both high gain and balancing helps lower the overall distortion. Replacing the collector resistor of the gain stage (Q3) with an Active Load (Q10) raises the voltage gain and provides better current drive to the positive half of the output buffer. Driving a low impedance like 8 ohms demands a lot of current from the output buffer. A Darlington Output Buffer helps deliver the current and minimize the load on the gain stage. This keeps the overall gain high and the distortion low. – Advanced Audio Amplifier CIRCUIT INSIGHT Let`s check the bandwidth. Does it meet the 600kHz calculated above Run an AC Analysis and plot the output V(20). What happened to the bandwidth It seems to have fallen dismally short of 600 kHz! Turns out, the problem lies in the output stage. Because it`s biased class B, the output transistors are essentially OFF when the output is near 0V. What`s the remedy I`ve snuck in a voltage source VOFF at the base of Q2. A small voltage here will offset the output by the same voltage. Hopefully, a few tenths of a volt will turn ON the output stage. Temporarily set VOFF to 0. 5V and rerun the AC analysis. How high is the bandwidth now Set VOFF back...




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Balanced microphone preamp project
Proximity detector
Laser-diode-pulsers
Hee-haw-slren
Summing-amplifier-clamping-circuit
Precise One Shot Circuit
LM723CA31402N3055 Variable Regulator 0-30V 5A
18W Audio Amplifier Circuit
A simple DDS for 136kHz
Monostable Multivibrator
Bicycle speed circuit
20W + 20W stereo amplifier circuit diagram
Has 50 times the pre-amplified bridge circuit diagram XTR106



Top