An operational amplifier (op amp) is an analog circuit block that takes a differential voltage input and produces a single-ended voltage output. Op amps usually have three terminals: two high-impedance inputs and a low-impedance output port. The inverting input is denoted with a minus (-) sign, and the non-inverting input uses a positive (+) sign.
The op amp has high impedance and low output impedance in the voltage follower configuration so it functions as an impedance matching circuit. So if the opamp's supply is 5volt, the output of the opamp can only swing between (almost) 0volt and ~3.5volt. About 700-720 A/D values.
In the book “OP AMP APPLICATIONS” (Analog Devices, edited by Walt Jung) the use of (op amps and) audio transformers in line input and output applications are discussed in depth. In particular the mixed feedback drive circuits for line output transformers are analyzed in great detail.
Using The Complex Impedance Approach, Find The Transfer Function Vo(s)/V/(s) Of The Op-amp System Shown And Demonstrate That The System Is A Noninverting Amplifier. Apply The Result To Calculate The Transfer Function Of The System In Terms Of R1, R2, L, And C. Plot The Output Voltage Of The Op-amp Circuit Of Shown Using The Transfer Function Vo ...
2.6 Op-amp Imperfections in the Linear Range of Operation. Input Impedance and Output Impedance. Input impedance • BJT input stage: > 100kΩ, typically few MΩ; • FET input stage: ~10. 12. Ω. Output impedance: ~100Ωor less. If the gain the Op Amp is high, the influence of the input and output impedance is small.
Taking the op-amp's output voltage and coupling it to the inverting input is a technique known as negative feedback, and it is the key to having a self-stabilizing system (this is true not only of op-amps, but of any dynamic system in general). This stability gives the op-amp the capacity to work in its linear (active) mode, as opposed to ...
The open-loop output impedance of an op-amp is a complex affair. But in the case of the LM386, which is designed to drive a loudspeaker, the short answer will be "as low as possible". Perhaps just a couple of ohms. Why don't you measure it?