Why cant a function generator output 100mA?

Thread Starter

Bakez

Joined Aug 21, 2012
31
How did u get 70milli amps? Im looking at pulse data

I dont understand why it cant output 100ma although my gut instinct says it wont

PULSE
Frequency Range: 500 µHz to 12.5MHz (TG2511 - 500 µHz to 6.25MHz)
Resolution: 1µHz , 14 digits
Output Level: 10mVp-p to 10Vp-p into 50 Ω
Overshoot: <5%
Jitter: 300ps + 0.01% of period
Rise/Fall Times: Rise and Fall times can be independently varied or can be varied
together simultaneously.
Edge Range: <8ns to 40µs (TG2511 - <13ns to 40µs)
Edge Resolution: 0.1ns for rise/fall time ≤100ns; 1ns for rise/fall >100ns and ≤2µs;
10ns for rise/fall >2µs and ≤40µs
Width Range: 20ns to 2000s (20ns minimum for period ≤40s; 200 ns minimum for
period >40s and ≤400s; 2µs minimum for period >400s)
Width Resolution: 10ns for period ≤40s; 100ns for period >40s and ≤400s;
1µs for period >400s
Delay Range: 0ns to 2000s
Delay Resolution: 10ns for period ≤40s; 100ns for period >40s and ≤400s;
1µs for period >400s
 

studiot

Joined Nov 9, 2007
4,998
How did u get 70milli amps? Im looking at pulse data
I did the calculations, that anyone contemplating such an instrument should be able to do.

This is a function generator and to output a sine wave:

10V pk-pk = 5 volts peak = 5/√2 volts rms.

5/√2 volts into 50 ohms gives 5/√2*50 amps rms.
 

Thread Starter

Bakez

Joined Aug 21, 2012
31
Yes that is for a sine wave

For a 5V pulse, it should be able to do 100mA, if I just use the same calculation you have?
 

hexreader

Joined Apr 16, 2011
471
I set my function generator to square wave 0.1 Hz 10V p-p

A multimeter directly across the output reads 93 mA for 5 seconds, then -87 mA for 5 seconds.

Seems pretty close to 100 mA to me.

Of course, the average DC current is close to 0 mA.

10V p-p sine wave (3.5v RMS) 50Hz gives 63mA RMS AC, which sounds about right to me.

I see no inconsistency in my experiments.

I agree that a 5V pulse should (and probably does) give 100mA for the time the pulse is at 5V, but average current will be much less if you count the off time.

How are you measuring current? Most multi-meters expect pure DC on the DC range, then 50 or 60 Hz sine wave on the AC range. Anything else, and a cheap multimeter is likely to give false readings.
 
Last edited:

wmodavis

Joined Oct 23, 2010
739
If its outputting 5V and has 50ohm output impedence then surely its outputting 100mA also?
Your figuring seems to be amiss.
Output current is not only determined by the device output impedance but the load impedance. If you shorted the output is may put out 100mA.
 
Top