How an Amplifier Drives a Capacitive Load

How an Amplifier Drives a Capacitive Load

Consider a single pulse = one rise and one fall
Charge transfer on each transition = C_Ioad •ΔV_out = l_rise •T_rise = l_fall•T_fall
Energy dissipated in Q_high = average voltage • current• time
                     =(V_bus-V_{out_avg})•l_rise •T_rise
                     =(V_bus-V_{out_avg})•C_Ioad •ΔV_out
Energy dissipated in Q_low = average voltage• current• time
                     = V_{out_avg} • l_fall•T_fall
                     = V_{out_avg} •C_Ioad •ΔV_out
Total energy dissipated in Q_high and Q_low = (V_bus-V_{out_avg})•C_Ioad •ΔV_out + V_{out_avg} •C_Ioad •ΔV_out
                               = C_Ioad •V_bus•ΔV_out
For repeated pulses;
Total power dissipated in Q_high and Q_low = C_Ioad •V_bus•ΔV_out•frequency
Example:100pF•2500V•400V•20kHz=2W

Thanks for Ed Solomon, Triple Ring Technologies Inc.

Keywords: high voltage amplifier, high voltage amplifiers, high speed high voltage amplifier

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