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Need Clarification On This Power Amp Circuit...
- Thread starter Sentrec
- Start date
cesarcesar
Electrical
I confirmed the IC 5534 is a high speed op amp,
Product Name NE5534
Product Type Operational Amplifier (Op-Amp)
Supply Voltage +/- 3V to +/- 22V
I believe the circuit is INCOMPLETE.... There is no feedback.
The circuit should not apply the input signal from v+ to v- (and then have the op-amp open loop gain of (~6000) multiply the input to produce an output.
Yes, CR1 and CR2 (help turn on Q1 & Q2 to prevent transistor crossover dist), but the Vdrop of CR1 and CR2 may barely be enough to bias on Q1 and Q2 given the size of R4 and R5....
looseelectron
Electrical
This is a classic AB amplifier design.
Some insights:
CR1, CR2, CR3, CR4 exist to keep the bias of the base of Q1 and Q2 two diode drops apart, or to be more specific, two Vbe junction drops apart. The reason for two sets of diodes is to maintain that bias voltage when the input voltage transitions are positive or negative.
If this is set up as a module, a feedback resistor network needs to be added from the output (pin 1, on the right) to the negative input of the op-amp (pin 3 on the left)Two resistor feedback net will establish overall gain, and will help improve the linearity of the output stage.
The output can source current into the load (Q1 on and pumping out current) or sink current out of the load (Q2 on)
Crossover behavior (As Q1 shuts down and Q2 turns on, or vice versa) can be a little glitchy, and the feedback amplifier feedback that include the AB amplifier in the loop helps with that, within the bandwidth limitations of the op-amp.
These were commonly used in audio amplifier designs back in the 1960-1980 era, before Class D switching amplifiers started to dominate audio amplifier design.
Jerry Twomey, Author of:
"Applied Embedded Electronics
Design Essentials for Robust Systems"
Some insights:
CR1, CR2, CR3, CR4 exist to keep the bias of the base of Q1 and Q2 two diode drops apart, or to be more specific, two Vbe junction drops apart. The reason for two sets of diodes is to maintain that bias voltage when the input voltage transitions are positive or negative.
If this is set up as a module, a feedback resistor network needs to be added from the output (pin 1, on the right) to the negative input of the op-amp (pin 3 on the left)Two resistor feedback net will establish overall gain, and will help improve the linearity of the output stage.
The output can source current into the load (Q1 on and pumping out current) or sink current out of the load (Q2 on)
Crossover behavior (As Q1 shuts down and Q2 turns on, or vice versa) can be a little glitchy, and the feedback amplifier feedback that include the AB amplifier in the loop helps with that, within the bandwidth limitations of the op-amp.
These were commonly used in audio amplifier designs back in the 1960-1980 era, before Class D switching amplifiers started to dominate audio amplifier design.
Jerry Twomey, Author of:
"Applied Embedded Electronics
Design Essentials for Robust Systems"
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