Description of the problem
When working with Charge amplifiers, we might be interested in the Time constant, which is a crucial parameter that determines how quickly or slowly a system reacts to change. It affects both the frequency response and the time-domain behaviour of the amplifier.
You might have noticed this parameter when looking at the DSI-CHG-DC specifications, where we list both the filter and the time constant, but we do not list them for our CHG amplifiers.
This solution will quickly go over the calculations of this constant.
Description of the solution
The time constant of an RC circuit can be defined as
τ=R⋅C
where τ = time constant, R = resistor, C = Capacitor
and it describes the time it takes for a signal to rise or decay to about 63.2% of its final value in response to a step change.
Another way to describe the time constant is through the cutoff frequency (f_c) of a filter
τ=1/(2π * f_c)
The calculations are then simple.
Example:
For the SIRIUS HS-CHG, the Input coupling specifications are as follows:
If our Input coupling is set to 0.01 Hz, the time constant will be:
τ=1/(2π * f_c) = 1/(2π * 0.01 Hz) > 15 s