Calculating integrator gain

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Some clarification is obviously needed for this “short pulse” trick. Just increasing operating frequency, keeping pulse width unchanged will increase sensitivity (more samples integrated) but current consumption will rise proportionally, so compromise is needed at some point. Short TX pulse is one, good for surf-like and similar detectors, intended for small targets, coin sized or smaller, jewelry, small gold etc. Anyway, short decay targets, so short TX is enough to excite them. On larger detectors, like delta etc, whit larger coils, intended to find larger objects (longer decay), too short pulses are ineffective and you will lose range (actually, short pulse detectors are less sensitive to larger objects, end range to large metal sheet or sensitivity to cola can is smaller compared to unmodified classic detector, just not intended for such targets). Even whit delta, some limit exist, in most cases anything above 150-200uS is waste of power too, except for barrel drum hunting and 1m loop. Best compromise is to keep not too excessive pulse width and increase freq. until power consumption is still reasonable.
I never modified GS4, but GS5 is already at 3.7kHz and unchanged, 100uS long pulse.

Integrator time constant define detector response time, no need to change it if you change frequency.

So, short pulse (20-30uS) high freq. as i described before works best for some target types, not good for some other, but in general, shortest pulse for given target and highest freq. limited by power consumption is the best compromise. (also, in any detector whit N type transistor, you can try something better than IRF740, for example Toshiba 2SK2611 is relatively cheap and available)

I ordered some of these 2SK2611 and they arrived today, they are a very big case much bigger than 740. 900v coss 190pF

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Integrator out=integrator gain*average input signal during sample. Think I know how to calculate average signal for a straight line decay on a linear X linear Y chart. Is there a formula for calculating average in for straight line decay on linear X log Y and log X log Y charts?

Integrator out opposite polarity average signal in. First example should be -175