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Here I present my 2'nd year university physics project, undertaken while at Imperial College, London university. Unlike the 1'st and 3'rd year projects, which were my own proposals, this one was selected in the more usual way from a list of undergraduate projects provided by the physics department.

Although this is a biophysics project, as usual my main interest was in the electronics. The part of which I am most proud is the innovative Automatic Gain Control (AGC) circuit, without which the project would not have succeeded. This AGC circuit could well be used in many other applications too.

Unfortunately I have no photographs. Where you see a diagram in the report, you can click it to see an larger image.

Click here to start reading from the beginning...

CONTENTS.

1. Introduction.

2. Background Information.
    2.1 Muscle structure and contraction.
    2.2 Monochromatic light diffraction experiments.
    2.3 X-ray diffraction experiments.
    2.4 The need for a positive feedback circuit.

3. Design Solution.

4. Detailed circuit description.
    4.1 Detectors.
    4.2 Pre-amplifiers.
    4.3 First difference amplifiers.
    4.4 Automatic Gain Control (AGC).
    4.5 Final Difference amplifier.
    4.6 Power Supply

5. Testing of the device.
    5.1 Static testing: longitudinal.
    5.2 Static testing: transverse.
    5.3 Dynamic testing.
    5.4 AGC Circuit response.

6. Conclusion.

APPENDIX: Connections and Layouts.