Suppose I have a circuit which gets damaged for spikes and high voltages, so that I need to eliminate spikes and high voltages beyond a maximum value, so I have decided for the following two configurations for my circuit. Please tell me which one would act as the best voltage protection for my circuit
simulate this circuit – Schematic created using CircuitLab
In the first one, I use an opamp as a voltage buffer and let my max allowable input be Vmax-u, where u is a small tolerance I use for safety, but in the second one I first use a Low pass filter to get rid of spikes and then I use a transistor circuit which when biased beyond Vmax, would ground the voltages.
Best Answer
You did not specify how large your input signal is and how large are the "spikes and high voltages". If your input signal is below say 0.5 volt peak, then you can use back-to-back diodes connected from your input to ground. The diodes will not conduct for the signal and thus appear as high impedance devices but will conduct for anything above about 0.7 volts. If your signal is above 0.5 volt, you can bias the diodes to compensate. For very fast spikes, as already pointed out, you may need a device designed just for that such as a transient voltage suppressor or even a spark gap. You really need to specify your voltage levels and the source impedance of the signal and the interfering signals before a more definitive answer can be given.