How to power an OP amp, please if I am not correct, comment.
Ok here is my understanding of the above circuits. Please correct me if I am wrong for my own sake and for anyone else reading this, I am learning as I go on this one, which is how I ended up on this thread.
In the single supply side diagram on the left there is a voltage divider coming off the power with 22k resistors, and the voltage in the center of the divider is Vcc/2. This is called the bias voltage.
There is another resistor R3 on the single supply circuit (and R2 on the dual supply circuit) of 22k. In an ideal situation, the op amp has an arbitrarily high input resistance so the DC current flowing into the op amp is zero and the DC current flowing across R3 is also close to zero. Therefore the voltage drop across R3 is zero. This means the Voltage at R3 or the input of the is just the bias voltage.
When you couple AC signal (call it v) to the bias voltage of Vcc/2 at the voltage input +, you get an output of Vcc/2 with a superimposed signal of about 20*v on top of the DC bias of Vcc/2. In other words, the AC signal "rides along" on top of the DC bias voltage. Then at the ouput, you decouple the AC signal from the DC signal with a capacitor.
On the example to the right, all the same logic applies, but the DC bias voltage is set at zero with R2, and you get the ac input signal is riding on zero. The output signal ~20v is riding on zero so there is no need for a decoupling capacitor ideally.
Furthermore, this bias voltage Vcc/2 created at the voltage divider (for the single supply, and zero on the dual supply), can be "tapped into" to set the bias voltage of op amps elsewhere in the circuit if needed in the same manner. It does not need rebuilt for each and every op amp in the circuit.
Ok here is my understanding of the above circuits. Please correct me if I am wrong for my own sake and for anyone else reading this, I am learning as I go on this one, which is how I ended up on this thread.
In the single supply side diagram on the left there is a voltage divider coming off the power with 22k resistors, and the voltage in the center of the divider is Vcc/2. This is called the bias voltage.
There is another resistor R3 on the single supply circuit (and R2 on the dual supply circuit) of 22k. In an ideal situation, the op amp has an arbitrarily high input resistance so the DC current flowing into the op amp is zero and the DC current flowing across R3 is also close to zero. Therefore the voltage drop across R3 is zero. This means the Voltage at R3 or the input of the is just the bias voltage.
When you couple AC signal (call it v) to the bias voltage of Vcc/2 at the voltage input +, you get an output of Vcc/2 with a superimposed signal of about 20*v on top of the DC bias of Vcc/2. In other words, the AC signal "rides along" on top of the DC bias voltage. Then at the ouput, you decouple the AC signal from the DC signal with a capacitor.
On the example to the right, all the same logic applies, but the DC bias voltage is set at zero with R2, and you get the ac input signal is riding on zero. The output signal ~20v is riding on zero so there is no need for a decoupling capacitor ideally.
Furthermore, this bias voltage Vcc/2 created at the voltage divider (for the single supply, and zero on the dual supply), can be "tapped into" to set the bias voltage of op amps elsewhere in the circuit if needed in the same manner. It does not need rebuilt for each and every op amp in the circuit.
Your description of the bias voltage is essentially correct. You can also use one bias voltage generator to bias more than one amplifier providing that the bias generator is not going to have its voltage altered by the incoming audio signal. That means the bias generator needs to present as a low impedance... and with C2 being large it does. That may still not be good enough for purists though.
In the single rail design the incoming signal modifies or alters the bias voltage as you say.
One golden rule will help you understand how all these amplifiers work... why they have the gain they do... and why they behave as they do. This rule applies to inverting and non-inverting designs and covers any opamp configured 'with feedback' which in practice means any audio application.
RULE The output of the opamp will do whatever it takes to bring the difference in voltage as seen between the inputs to zero. Notice the word difference.
Edit... although I know what you mean, the output voltage doesn't ride on zero, more correctly it moves away from zero in response to the input signal. You can't simultaneously have two voltages at one point at any given moment in time. In the case of the single rail, it moves away from the Vcc/2 point in response to the input signal.
In the single rail design the incoming signal modifies or alters the bias voltage as you say.
One golden rule will help you understand how all these amplifiers work... why they have the gain they do... and why they behave as they do. This rule applies to inverting and non-inverting designs and covers any opamp configured 'with feedback' which in practice means any audio application.
RULE The output of the opamp will do whatever it takes to bring the difference in voltage as seen between the inputs to zero. Notice the word difference.
Edit... although I know what you mean, the output voltage doesn't ride on zero, more correctly it moves away from zero in response to the input signal. You can't simultaneously have two voltages at one point at any given moment in time. In the case of the single rail, it moves away from the Vcc/2 point in response to the input signal.
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