This amplifier is used to control an electro-pneumatic actuator. Let me describe it a little bit:
- the input voltage (the control signal) is V3 (-30V < V3 < +30 V)
- the output is at two pins of C8 (or two anodes of P3 and P4);
- There are two stages: stage 1 includes P1 and P2, stage 2 includes P3 and P4. When the input V3 changes, the voltage difference between two anodes of P1 and P2 changes correspondingly. The signal is sent to stage 2 through voltage dividers R6-R7 and R8-R9.
- Z1 and Z2 represent two coils inside the electro-pneumatic actuator. When the actuator moves, it constantly feeds a singal back, represented by V4.
- V1 and V2 are constant voltage sources, V1 = -150V ; V2 = +150V ;
The whole purpose of this amplifier is to keep V4 = V3. In the other word, for example, if we set V3 = 10V, then the actuator will move so that its feedback V4 = 10V.
The pentodes used in the diagram are 6Ж5Б-B, which has following properties:
I would like to know how this circuit works. I put this on LTSpice but it doesn't work because LTSpice does not have pentode models, just icons. I put some pentode models that I downloaded from Internet but it still doesn't work, one of the reasons is the models are not 6Ж5Б-B.
So I decide to understand this by hand-calculation using the characteristic curves of 6Ж5Б-B. For example, what are the current in the anodes of P1 and P2 when V3 = 10V? Even more, what are the purpose of C3 ; R12 and R13 ; R29 and C9 ; C8...?