One of the main design parameters is the stage's transconductance, given by the power bandwidth required on the amplifier.
Always number Audio amplifier project the parts. Then it is easy to discuss the diagram. Instead of "the emitter resistor of the second transistor" we just say R5. This is a coupling capacitor which allows the AC signal to pass but blocks DC. It protects the microphone's coil from receiving a DC current from the amplifier's bias circuit and protects the amplifier's bias circuit from being disturbed by the impedance of the microphone.
C1 transmits the voltage fluctuations from the microphone, superimposing them upon the bias voltage between R1 and R2. These resistors form a voltage divider, establishing a voltage-divider bias for the base of transistor Q1.
From a 9V power supply, R2 will develop about 1V. That's enough to forward bias the base junction of Q1, turning the transistor on. Its job is to transform variations in the base current caused by the microphone voltage variations arriving over C1 into current variations through the collector-emitter circuit R3, R4 and C2.
This is the load resistor for the CE voltage amplification stage. Variations in current controlled by Q1 cause R3 to develop a voltage.
This voltage is the output of the Q1 stage, directly conveyed to the base of Q2. The voltage is inverted with respect to the microphone signal. When the signal swings positive, more current flows through R3, developing a greater voltage drop.
The top of R3 is pinned to the 9V power rail, so more voltage drop means that the bottom of R3 swings more negative.
This emitter resistor provides feedback to stabilize the DC bias of Q1. The bias provided by R1 and R2 turns on Q1 using a voltage of about 1V, mentioned above. This causes current to flow through the transistor.
This current causes a voltage in R4. The transistor "rides" on this voltage. So the voltage opposes the 1V of bias. According to some rule of thumb calculations, R4 will develop about 0.
This bias current also flows through the 10K R3 resistor, where it gives rise to a voltage of 2V. So the output of Q1 is biased approximately 2V below the 9V power rail. This capacitor bypasses the R4 resistor for AC signals. The R4 resistor has the effect of feedback.
The amplified current passes through R4 and develops a voltage, and Q1 rides on top of this voltage. The voltage being amplified is the difference between the input and the emitter.
So R4 provides negative feedback, which reduces gain. By introducing C2, we get rid of this feedback for AC signals. AC signals do not experience negative feedback, and so the gain is much higher for those signals. R3 and R4 provide a stable DC bias for Q1, and C2 "cheats" around it, creating a higher gain for AC, so that the amplifier has a wider swing around the bias point which, recall, is about 2V below the power rail.
A lot of voltage gain is needed because microphones put out a rather small signal, and all the amplification is being done by a single stage. This transistor is set up as a current amplifying emitter-follower stage.This audio amplifier module can be used to play your FM receiver kit, make infrared based music transmitter and receiver, etc.
DOWNLOAD THE DATASHEET OF LM Project on mini breadboard. This bundle includes 30 assorted kits so that each student can work the project start to finish. O $ $ Only 9 in stock Digital Audio to Analog Converter.
Catalog #: Digital Audio to Analog Converter this mini audio amplifier is perfect for many acoustic projects. Also includes a microphone input and a speaker. The analog audio output of the RPi is connected to one of the original amplifier inputs.
This now enabled the amplifier to now also be a convenient music player, connected to both my NAS for the music file(s) source and connected to my main living room speakers. You are about to report the project "Amplifier project by Nutube, a new vacuum tube!", please tell us the reason.
Send message Hello, I really like your project and I think I have skills to help you. Feb 23, · The amplifier has five pentodes running in single-ended fixed bias with Edcor GXSEk output transformers.
the pentodes are driven by 12AT7's. in addition, i have made use of 12AU7's as pre-amplifiers for all 5 channels, plus a sub-woofer pre-amp for a external solid state amplifier.
DiscoverCircuits has 45,+ free electronic Electronic Circuits or Electronic SchematicsAudio Preamplifier circuits, schematics or diagrams. Power Amplifiers Audio Circuits -- Main Page Audio (DoZ) Class-A power amp (Project 36), and has very low levels of noise and distortion, in a minimum component count, fully discrete circuit.