- 1). Simplify the circuit design so that it reduces to an equivalent RC circuit, where R and C represent equivalent resistance and capacitance, respectively. A circuit design, also known as circuit schematic, represents how all components are joined together.
For equivalent resistance, add all resistors connected in series using R(series)=R1+R2+..... For resistors connected in parallel, use the formula 1/R(parallel)=1/R1+1/R2+....
For example, suppose there are two resistors in series with values 10 Ohm and 20 Ohm, and two in parallel with values 100 Ohm and 100 Ohm. The series equivalent will be R(series)=10+20=30 Ohm. The parallel equivalent will be 1/R(parallel)=1/100 + 1/100=1/50. This gives R(parallel)=50 Ohm. Now, assume that these equivalent resistances are in series. This gives the overall equivalent resistance as R(equivalent)=R(series) + R(parallel)=30+50=80 Ohm. Similarly, calculate the equivalent capacitance, only with the order reversed. That is, add the capacitors in parallel: C(parallel) = C1+C2+..... For the ones in series, use the formula 1/C(series) = 1/C1+1/C2+..... - 2). Multiply the equivalent resistance and capacitance together, then multiply the result by 4. Call this U, as in U = 4xR(equivalent)xC(equivalent).
- 3). Take the reciprocal of U. That is f=1/C. This is the required noise bandwidth in Hertz of the equivalent RC circuit.
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