Circuit Headphone Amplifier OPA134PA
The Headphone
amplifier circuit is based on a combination of the op amp and output stage with two transistors, capable of delivering power to feed the headphones comfortably.
The input is on the inverting terminal of the op amp U1, through resistor R1 and a part of the gain adjustment potentiometer in RV1. Input impedance is high enough to allow the retribution at each line output level of AF without fear of interference, as long as it still remains that the output impedance of the circuit in which you will not connected to 2 KOhm or 4.7
This environment is achieved through the presence of the two
resistors R2 and R3 of the same value, which form a voltage divider bridge, we are dealing with a virtual ground. The capacitor C1 guarantee a good stability to the reference voltage. The voltage thus generated can be found at the output, and should definitely not reach the earphones of the headset. This is the reason for the presence of the coupling capacitor C2, which passes only useful AC signal.