33120A: Maximum Output Current

Output current is not a specified parameter, however, a single unit was characterized to determine its performance. The maximum output current was 139mA RMS, with the 33120A configured for a 10Vp-p, 1 kHz sine wave. The 33120A output was fed directly into the current inputs ( approx 0.5 ohm) of a 34401A DMM. The output current reading decreased linearly to 14mA RMS as the output voltage setting was decreased to 1Vp-p.The 33120A is designed for a 50 Ohm load, and includes a 50 Ohm matching resistor in series with the final output stage. A portion of the output voltage is dropped across this internal resistance. This voltage drop increases as the load resistance decreases. When the 33120A output is set to 10 Vp-p, 139mA RMS was delivered to the low load resistance of the meter. The majority of the output voltage was dropped across the 50 Ohm resistor internal to the 33120A, with only a small portion appearing across the load. No attempt was made to measure distortion that might be caused by the impedance mismatch.Revision 1.1 18 JAN 00 gfe