. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. CRYSTAL OSCILLATORS between grid and earth, and between anode and earth. Putting these in {Figure ) and remembering that the crystal is to act as a parallel tuned circuit, we see that we have a modified Colpitts oscillator in which some of the tuning capacitance is direct across the coil and some of it is split, Colpitts- wise, to effect the virtual tap on the tuned circuit {Figure ). The output from a Pierce oscillator can be taken out directly to a high- impedance load such as
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. CRYSTAL OSCILLATORS between grid and earth, and between anode and earth. Putting these in {Figure ) and remembering that the crystal is to act as a parallel tuned circuit, we see that we have a modified Colpitts oscillator in which some of the tuning capacitance is direct across the coil and some of it is split, Colpitts- wise, to effect the virtual tap on the tuned circuit {Figure ). The output from a Pierce oscillator can be taken out directly to a high- impedance load such as another valve as shown, or by electron coupling, in which case the oscillator circuit undergoes the same kind of transformation that occurred between Figure and The circuit as published will have the appearance of Figure , but a truer representation is Figure The purpose of the choke inductance is to carry the cathode current while allowing the cathode to be an active electrode driven by the stray capacitances as shown. As usual with electron coupled schemes the purity of the output is poor and the anode load is often made a tuned circuit, where this matters. TATG oscillator This has the form of Figure , from which it will be seen that an LC tuned circuit is required as well as the crystal, but the circuit has the merit of giving rather greater output. The mode of operation is complicated; the name arises from an equivalent LC oscillator which is of little interest to electrobiologists and has not been mentioned, the tuned anode, tuned grid {Figure ). The feedback is via the valve grid-anode capacitance, and can HT+. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Donaldson, Peter Eden Kirwan. New York, Academic Press
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