KhalDirth
Electrical
- Aug 11, 2009
- 8
Hello All,
I am analyzing a signal mixing circuit that belongs inside of a generator voltage regulator. The mixing circuit is part of the feedback loop for controlling generator output voltage onto the system. A part of the circuit is a bit confusing to me. It involves diodes and transistors. While I am used to working with both seperately, together I am not sure as to how they work together.
In the schematic, the output voltage is going into an inverted op-amp (type 741) with a gain of -1. The schematic information book reads as follows:
"Inputs C and D are "auctioneering" inputs, in which the most positive of the two signals is given control.
A negative signal at Input A will override any signals present at the other inputs (note: Input A is considered a "limiting" circuit)."
To make things easier, Input B is usually riding around 14 Vdc.
I guess my questions are:
1) How does Input A override all other inputs?
2) I believe that if Input B were to change, it would override. Is this true?
3) Are the transistor amplifier circuits used to prevent overloading of the diodes? They seem to always be gated on, so I'm not sure of their purpose.
I am aware of how an auctioneering circuit works, but usually just in a diode-OR function, not in parallel with "limiting" circuitry and NPN transistors.
Any help is appreciated!!
Sincerely,
Mario Capuozzo
Associate Engineer
I am analyzing a signal mixing circuit that belongs inside of a generator voltage regulator. The mixing circuit is part of the feedback loop for controlling generator output voltage onto the system. A part of the circuit is a bit confusing to me. It involves diodes and transistors. While I am used to working with both seperately, together I am not sure as to how they work together.
In the schematic, the output voltage is going into an inverted op-amp (type 741) with a gain of -1. The schematic information book reads as follows:
"Inputs C and D are "auctioneering" inputs, in which the most positive of the two signals is given control.
A negative signal at Input A will override any signals present at the other inputs (note: Input A is considered a "limiting" circuit)."
To make things easier, Input B is usually riding around 14 Vdc.
I guess my questions are:
1) How does Input A override all other inputs?
2) I believe that if Input B were to change, it would override. Is this true?
3) Are the transistor amplifier circuits used to prevent overloading of the diodes? They seem to always be gated on, so I'm not sure of their purpose.
I am aware of how an auctioneering circuit works, but usually just in a diode-OR function, not in parallel with "limiting" circuitry and NPN transistors.
Any help is appreciated!!
Sincerely,
Mario Capuozzo
Associate Engineer
