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
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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...
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....
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....
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....
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....
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,....
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....
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....
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.....
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to....
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