Zeners show non-linear capacitances high enough to affect high frequencies if source impedance is not very low
In order to clamp low level signals, zeners should be used only as continuously polarized voltage references, not directly as clamp elements, since the capacitance of the zeners by itself may be enough to unexpectedly clamp the signal while it gets charged
Thus, a much better aproach is generating a positive and a negative references through a zener to ground in series with a biasing resistor to the corresponding supply rail, and using 1N4148 diodes to clamp the signal. 1N4148 has much lower capacitance and faster 'switch' than any zener
In order to clamp low level signals, zeners should be used only as continuously polarized voltage references, not directly as clamp elements, since the capacitance of the zeners by itself may be enough to unexpectedly clamp the signal while it gets charged
Thus, a much better aproach is generating a positive and a negative references through a zener to ground in series with a biasing resistor to the corresponding supply rail, and using 1N4148 diodes to clamp the signal. 1N4148 has much lower capacitance and faster 'switch' than any zener
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