Patent ID: 9203356
Filing Date: 2015-12-01
Classification: H03F

Abstract:
1. A method for sensing, comprising: connecting an input of a trans-impedance amplifier (TIA) to a first terminal of a sensor, which has a capacitance between 0.1 and 2 pF and which generates a current in response to an input signal that is incident on the sensor, the signal comprising pulses of a characteristic duration; connecting a resistor, having a resistance between 1 and 500 kΩ, in series between a second terminal of the sensor and a power supply, which is set to drive the sensor at a selected voltage between 20 and 220 volts DC; connecting a capacitor, having a capacitance between 0.1 and 2 pF, to the second terminal in parallel with the sensor and the TIA and in series with the resistor; setting an upper limit on the current that is to be input to the TIA from the sensor; and choosing respective values of the resistor and the capacitor, responsively to the characteristic duration of the pulses and the selected voltage, so that the capacitor provides sufficient energy to enable the TIA to generate a pulsed output signal in response to the pulses of the input signal, while preventing the current input to the TIA from exceeding the upper limit, wherein choosing the values comprises identifying a desired voltage level and pulse duration of the pulsed output signal, and selecting the capacitor so that the energy stored in the capacitor is sufficient to provide the desired voltage level and pulse duration but is not sufficient to allow the current input to the TIA to reach the upper limit.