Operating Basics
40
P7380SMA 8 GHz Differential Probe Instruction Manual
Internal Probe Amplifier
The P7380SMA differential probe is designed to measure high
frequency, low-voltage circuits. Before connecting the probe to your
circuit, take into account the limits for maximum input voltage, the
common-mode signal range, and the differential-mode signal range.
For specific limits of these parameters, see Figure 17 on page 43 and
Specifications
starting on page 65.
Maximum Input Voltage.
The maximum input voltage is the maximum voltage to ground that
the inputs can withstand without damaging the probe input circuitry.
CAUTION.
To avoid damaging the inputs of the P7380SMA differen-
tial probe, do not apply more than
±
5 V (DC + peak AC) between
each input and ground. In addition, the maximum termination
resistor power must not be exceeded to avoid probe damage.
Maximum Termination Resistor Power.
The internal termination resistors can safely dissipate 0.2 W of
power continuously, which is the case for normal probe operation
without termination driver current overload. However, the probe will
be damaged if you apply more than 0.5 W of power through the
termination resistors for more than 5 minutes.
If you suspect your measurement application will approach these
limits, use the formulas that follow to calculate the power dissipated
by the termination resistors.
The power calculation formulas are based on the simplified model
shown in Figure 16 on page 42, which represents the signal at the
probe inputs. If a signal source with 50
Ω
source impedances is used,
the signal levels used should match the zero-ohm source impedance
model in Figure 16.