Looking at the circuit diagram it follows the classic op-amp with a long-tailed pair of NPN transistors driving a PNP gain stage and finally a complimentary emitter follower as an output buffer.

RC =1 at phase shift of 45°; hence, the gain for an RC section is 1/0.707. The op amp must have a gain greater than four because the gain of four sections is 0.25. The buffered RC sections in this ...

The ideal op amp — which we can’t get — has infinite gain and infinite input impedance. While we can’t get that in real life, modern devices are good enough that we can pretend like it is ...

As a service to our readers, we're providing the LTspice files used in Dr. Dyer's article on simulation of the 12AX7 and the K2-W vacuum-tube op amp. 1. The model for the K2-W is established as a ...