# Calculation of resistor and capacitor values

Taking the circuit from this question: Photodiode driver circuit, shown again as image: I am now wondering how to calculate the exact needed values for the different resistors and capacitors (in the image placeholder values were used). For the photo diode PD24-01-HS is used (with data sheet here: http://www.ibsg-st-petersburg.com/datasheet/PD/PD24-01-HS.pdf)

From the other question I already know that R2 and the diode are a RC coupled circuit, leading to (if I want to have a frequency of 3 GHz, and assuming that the negative bias voltage in worst case is -3 V) a necessary resistance value for R2 of approximately 40 Ohm. How big should now C2 be? And how big should C1 (which flattens the input voltage) be?

• C2 is largely determined by what isn't shown i.e. what the output connects to. – Andy aka Aug 3 '16 at 11:49
• When saying, BNC with 50 Ohm, how can I then calculate C2? – arc_lupus Aug 3 '16 at 11:50
• What is the lowest frequency you will want to transmit? – Andy aka Aug 3 '16 at 11:50
• Several kHz, or if possible, some Hz, no exact limit given. – arc_lupus Aug 3 '16 at 11:52
• @arc_lupus There is no ideal value if you don't give us any borders for the frequency, as it affects the required capacitor size. Typically the value for the cap will decrease when the required frequency is higher. – The amateur programmer Aug 3 '16 at 11:58