. Electronic apparatus for biological research . HT* Figure Figure If £ is derived from the HT supply and is, say, 250 V, and Fout is, say, 200 V, and / = 300 seconds 300 X 250 ^^^ ,. â r J CR = ;rzrz:â =375 megohm-microfarads The solution is of course to reduce E, but if we do this we reduce the virtual charging voltage AE and spoil the linearity. The Gibbs and Rushton refine- ment makes use of a 'bootstrap' circuit {Figure ). Any cathode-follower cathode will set itself up a few volts positive to its grid. Applied to this circuit, these few volts constitute our charging vol
. Electronic apparatus for biological research . HT* Figure Figure If £ is derived from the HT supply and is, say, 250 V, and Fout is, say, 200 V, and / = 300 seconds 300 X 250 ^^^ ,. â r J CR = ;rzrz:â =375 megohm-microfarads The solution is of course to reduce E, but if we do this we reduce the virtual charging voltage AE and spoil the linearity. The Gibbs and Rushton refine- ment makes use of a 'bootstrap' circuit {Figure ). Any cathode-follower cathode will set itself up a few volts positive to its grid. Applied to this circuit, these few volts constitute our charging voltage, E. Current flows into C via R from Fi cathode, but the concomitant small rise in grid potential as the stroke proceeds does not reduce the rate of charging because the grid potential rise is transferred to F^ grid and produces a similar increase in E, maintaining the charging current. If we can by this method, without impairing the linearity, reduce E from 250 V to 2-5, we can secure a 5 minute sweep with CR = 3-75 megohm-microfarads, say C = OT microfarad and R = 37-5 megohms, both reasonable values.
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