waveboy
Electrical
- Mar 19, 2006
- 66
Dear Engineers,
I recently had an interview for an RF job and I was asked to analyse a circuit that provided the biasing power supply for an RF GaSFET. (i.e. they showed me the circuit diagram and then i had to explain how it worked)
I would now like to get hold of a similar circuit diagram and would be most grateful if anyone could suggest a web link which may contain this circuit diagram....
The circuit basically uses a linear regulator to provide the regulated voltage to the GaSFET. The voltage supply rails to the FET were at +10V and -10V.
However, in detail the circuit was as follows:-
Firstly, an oscillator using a 555 IC produced a square wave voltage at 100KHz, (i'm afraid that i cannot remember the voltage peak or average level of this square wave). This square wave was then amplified by a push pull amplifier which gave current amplification to the square wave and acted as a buffer.
The square wave was then fed to a diode network which basically produced the positive and negative supply rails. (This was done by having one diode inserted so that it was forward biased by the positive peak of the square wave and a different diode positioned so that it was forward biased by the negative peak of the square wave. -These diodes thus provided the separate positive and negative supply rails)
I am fairly certain that the linear regulator was placed in the negative rail.
Incidentally, there was also a 'protection' network (using transistors) that made sure that the positive supply rail could not 'power up' without the negative rail already being 'powered up' (since just having the positive rail 'powered up' was not good for the GaSFET)
I apologise for my bad recall of the circuit. However, I wondered if my explanation "rings any bells" with reading Engineers?
-If so, then I would be very grateful for any weblinks which give any details of this type of circuit, or give a similar circuit diagram. Also, any better description of the circuit (if known) would be most gratefully appreciated.
I recently had an interview for an RF job and I was asked to analyse a circuit that provided the biasing power supply for an RF GaSFET. (i.e. they showed me the circuit diagram and then i had to explain how it worked)
I would now like to get hold of a similar circuit diagram and would be most grateful if anyone could suggest a web link which may contain this circuit diagram....
The circuit basically uses a linear regulator to provide the regulated voltage to the GaSFET. The voltage supply rails to the FET were at +10V and -10V.
However, in detail the circuit was as follows:-
Firstly, an oscillator using a 555 IC produced a square wave voltage at 100KHz, (i'm afraid that i cannot remember the voltage peak or average level of this square wave). This square wave was then amplified by a push pull amplifier which gave current amplification to the square wave and acted as a buffer.
The square wave was then fed to a diode network which basically produced the positive and negative supply rails. (This was done by having one diode inserted so that it was forward biased by the positive peak of the square wave and a different diode positioned so that it was forward biased by the negative peak of the square wave. -These diodes thus provided the separate positive and negative supply rails)
I am fairly certain that the linear regulator was placed in the negative rail.
Incidentally, there was also a 'protection' network (using transistors) that made sure that the positive supply rail could not 'power up' without the negative rail already being 'powered up' (since just having the positive rail 'powered up' was not good for the GaSFET)
I apologise for my bad recall of the circuit. However, I wondered if my explanation "rings any bells" with reading Engineers?
-If so, then I would be very grateful for any weblinks which give any details of this type of circuit, or give a similar circuit diagram. Also, any better description of the circuit (if known) would be most gratefully appreciated.
