# Maximum voltage generated by a function generator

Discussion in 'General Electronics Discussion' started by Emam, Oct 3, 2014.

1. ### Emam

63
4
Jul 7, 2014
Hello,
I have a very basic question (since I am not familiar with generators !).
I would like to buy an arbitrary function generator (like Agilent 33210A).
In the data sheet of this generator its written that the generated voltage is 10 Vpp for 50 ohm charge résistance.
So, I want to know if I connect a very larger resistance (such as 8 Mega ohm) to this generator, what will happen? Can I have for ex a square pulse of 7 Volt amplitude on my resistance?
Because I mean do they have a something like "current regulators" inside?

2. ### BobK

7,682
1,688
Jan 5, 2010
I think what it means is that the voltage is 10V with an internal resistance of 50 Ohms. If you measure it with a 1M probe it would read 10V. If you put a 50 Ohm resistor across the output, the voltage would be cut exactly in half.

Bob

126
38
Apr 21, 2011
From the manual:

Amplitude

Range 10 mVpp to 10 Vpp into 50 Ω

20 mVpp to 20 Vpp into open circuit

Imagine the generator as providing +/- 10 Volts at maximum output, then imagine that there is an internal 50 Ohm resistor in series with the output connector. The ideal load would have 50 Ohms impedance, which is why terminated voltage is half of the open circuit voltage. The 50 Ohms internal impedance and the 50 Ohm load impedance work as a voltage divider to halve the output voltage.

8 Megohm load will barely drop the voltage at all. It is close to open circuit compared to the 50 Ohm Function Generator impedance.

If you want 7V across your 8 Megohm load, simply set the Function generator output to that (open circuit) value.

Last edited: Oct 4, 2014