. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. STIMULATORS of affairs by two potential dividers, R1R2 and R^R^, as shown in Figure We now put in the stray capacitances between A and B and the recording electrode, calling them Q and Co, and between A and B and earth, calling them C3 and C4, giving us Figure Finally, let the stimulator now become a constant-voltage pulse generator, of output E, and let the amplifier be replaced by its input impedance, Z, assumed to be relatively large {Figure ). The problem of minim
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. STIMULATORS of affairs by two potential dividers, R1R2 and R^R^, as shown in Figure We now put in the stray capacitances between A and B and the recording electrode, calling them Q and Co, and between A and B and earth, calling them C3 and C4, giving us Figure Finally, let the stimulator now become a constant-voltage pulse generator, of output E, and let the amplifier be replaced by its input impedance, Z, assumed to be relatively large {Figure ). The problem of minimization of stimulus artefact is now seen to be that of minimizing the out-of-balance current in a bridge circuit, but before. ©^ S '^a^is tTi (b) Figure attending to this it is worth remarking the nature of the unbalance current. It has three components: a transient of magnitude C, C. [Ci + Cg C3 -|- C4J a final value which it reaches if the pulse goes on long enough of magnitude ^ ii?l + i?2 i?3 + RJ and a phase between them which is the difference of two exponentials cor- responding to the time constants (^'+^^>(^J and (C3 + C4) ' RzR, ^ The observed artefact on the cathode ray tube face may have any of the forms in Figure —but only a, b, or c are at all likely. It is also worth noting at this point that the bridge cannot possibly be balanced if one side of the stimulator output is earthed, if R^ or 7?4 is zero. This puts all the 610. 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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