Hello everyone.
I've recently completed the practical work on a project that had to be developed from a set of specific requirements and a restricted parts palette.
To comply with the requirements of the project, my final design includes a single ended two transistor adaptive bias audio amplifier.
The amplifier is based upon a design published by Sir Douglas Hall, K.C.M.G., M.A., in the June 1973 edition of the Radio Constructor Magazine.
A version of Halls 'Sliding Junior' circuit was constructed, but it was found that its input impedance was too low to be of use in the project, ie. the input is unable to drive the adaptive bias circuit, and the output clips.
To circumvent the problem a follower could be added at the input, but to maintain the project transistor count to the limit in the specific, a feedback capacitor was added instead, so that the amplifier output would bootstrap the adaptive bias circuit effectively raising the input impedance.
So far so good.
The problem I have is that the working hardware has been presented along with the paper with the description of operation. The paper was returned, twice actually, with a note on this occasion that the tutor felt that the description of the amplifier was incorrect, particularly the claim that it was "bootstrapping" the adaptive bias diode clamp circuit, and that if I couldn't correctly describe the function of the circuit, he could only conclude that the hardware was not in any part my work.
The above is in essence my problem and the question is am I wrong? If so, how should I describe the method of operation. If on the other hand the tutor is wrong (and he refused to say how he thinks the circuit works), it will be catch 22 on getting no marks if I try proving it!
I've attached the circuit diagram of the amplifier as built.
Any opinions welcomed.
Thanks for reading,
Ami.
I've recently completed the practical work on a project that had to be developed from a set of specific requirements and a restricted parts palette.
To comply with the requirements of the project, my final design includes a single ended two transistor adaptive bias audio amplifier.
The amplifier is based upon a design published by Sir Douglas Hall, K.C.M.G., M.A., in the June 1973 edition of the Radio Constructor Magazine.
A version of Halls 'Sliding Junior' circuit was constructed, but it was found that its input impedance was too low to be of use in the project, ie. the input is unable to drive the adaptive bias circuit, and the output clips.
To circumvent the problem a follower could be added at the input, but to maintain the project transistor count to the limit in the specific, a feedback capacitor was added instead, so that the amplifier output would bootstrap the adaptive bias circuit effectively raising the input impedance.
So far so good.
The problem I have is that the working hardware has been presented along with the paper with the description of operation. The paper was returned, twice actually, with a note on this occasion that the tutor felt that the description of the amplifier was incorrect, particularly the claim that it was "bootstrapping" the adaptive bias diode clamp circuit, and that if I couldn't correctly describe the function of the circuit, he could only conclude that the hardware was not in any part my work.
The above is in essence my problem and the question is am I wrong? If so, how should I describe the method of operation. If on the other hand the tutor is wrong (and he refused to say how he thinks the circuit works), it will be catch 22 on getting no marks if I try proving it!
I've attached the circuit diagram of the amplifier as built.
Any opinions welcomed.
Thanks for reading,
Ami.