Driving Capacitive Loads

Amplifier Calculator Software

To help you select the appropriate Trek amplifier, download the new version of Trek PC software which uses peak-to-peak voltage to help calculate values associated with driving capacitive loads: (Amplifier Calculator Software (Win Zip file). Click to download (We recommend creating a new folder for software application downloads.)

Procedure for Calculating Peak Current

Engineers at Trek have designed many amplifiers with various voltage and current levels which can be used to drive capacitive loads. The table below lists selected Trek Amplifiers with their voltage and current ranges. The internal capacitance of each amplifier is in the X pF (pico farad) column. To determine which Trek Model amplifier is most suitable for your application:

  1. Substitute the peak-to-peak voltage that will be applied to your load into the appropriate equation for driving capacitive loads with sine, triangle, or square waves. Use the table below to select the Trek amplifier with the appropriate voltage or current characteristics.
  2. Select the correct internal capacitance value for the selected Trek amplifier from the X pF (pico farad) column and substitute the value into the X pF variable of the equation.
  3. Substitute the capacitive value of your load (C load ) into the equation.
  4. Substitute the desired frequency f or rise time dt (square wave) of the output waveform into the equation.
  5. Solve for the peak current needed from the amplifier.

If the calculated peak current is equal to or less than the peak current range of the amplifier, the Trek amplifier will not be bandwidth limited due to output current limitations. For example, if the calculated peak current is equal to or less than 20 mA, the Model 20/20C will not be bandwidth limited due to output current limitations.

Application Notes
Refer to application note 6003 titled "Choosing the Correct Capacitive Load Amplifier" for futher information regarding driving capacitive loads.

Driving Capacitive Loads with Square Waves
I = (C load + X pF) dV/dt

where:

I = the peak current needed from the amplifier
C load = the load capacitance
X pF = the internal output capacitance of the amplifier ( in pico farads)
dV = the peak value of the square wave
dt = the rise time required
dV/dt = the slope of the rise/fall time

Trek Amplifier Capacitance Chart

Model X pF

Output Current
(DC or peak AC)

Output Voltage
(DC or peak AC)
50/12 34 pF ±50 kV ±12 mA
40/15 43 pF ± 40 kV ±15 mA
30/20A 50 pF ±20 mA ±30 kV
P0621P 57 pF ±20 mA 0 to +30 kV
P0621N 57 pF ±20 mA 0 to -30 kV
20/20C 60 pF ±20 mA ±20 kV
10/40A 60 pF ±40 mA ±10 kV
PD07016 60 pF ±60 mA DC
±300 mA peak AC
for 20 µs		 ±10 kV
664 110 pF ±20 mA ±10 kV
10/10B-HS 55 pF ±10 mA ±10 kV
610E 66 pF ±2 mA ±10 kV
PD05034 50 pF ±50 mA DC
160 mA peak AC
for 60 µs		 ±7.5 kV
609B-3 66 pF ±2 mA ±10 kV
5/80 70 pF ±80 mA ±5 kV
609E-6 50 pF ±20 mA ±4 kV
PZD2000A 400 pF ±200 mA DC or 
±400 mA peak AC 		±2 kV
623B 50 pF ±40 mA ±2 kV
677B 330 pF ±5 mA ±2 kV
2220 300 pF ±10 mA ±2 kV
2210 300 pF ±20 mA ±1 kV
PZD700A
(±700 volt range)		 270 pF ±100 mA ±700 V
PZD700A 
(1.4 k volt ranges)		 135 pF ±50 mA +1.4 kV or -1.4 kV
PZD700A M/S
(±700 volt range)		 530 pF ±200 mA ±700 V
PZD700A M/S
(1.4 k volt ranges)		 270 pF ±100 mA +1.4 kV or -1.4 kV
2205 300 pF ±40 mA ±500 V
601C 400 pF ±10 mA DC
±20 mA peak AC
±500 V or +1 kV or -1 kV
PZD350A
(±350 volt range)		 365 pF ±200 mA ±350 V
PZD350A 
(700 volt ranges) 		230 pF ±100 mA +700 V or -700 V
PZD350A M/S
(±350 volt range)		 730 pF ±400 mA ±350 V
PZD350A M/S
(700 volt ranges)		 460 pF ±200 mA +700 V or -700 V
2100HF 150 pF ±300 mA ±150 V
603 800 pF ±40 mA DC or
±80 mA peak AC 		±125 V or +250 V or -250 V

Driving Capacitive Loads with Triangle Waves
I = 2 f (C load + X pF) Vpeak-to-peak

where:

I = the peak current needed from the amplifier
C load = the load capacitance
X pF = the internal output capacitance of the amplifier ( in pico farads)
f = the maximum output frequency
Vpeak -to-peak = the peak-to-peak voltage applied to the capacitive load

Driving Capacitive Loads with Sine Waves
I = (C load + X pF) pi f Vpeak-to-peak

where:

I = the peak current needed from the amplifier
C load = the load capacitance
X pF = the internal output capacitance of the amplifier ( in pico farads)
pi = 3.14
f = the maximum output frequency
Vpeak-to-peak = the peak -to-peak voltage applied to the capacitive load


  • Products
  • Downloads
  • Technical Info
  • Applications
  • Sales & Support
  • News & Events
  • About Trek