Hello, my name is Ken of Agilent Technologies.
In this video I'd like to show you how to force high voltage by using voltage source which the output can be floated.
Let's see how we can double the output voltage of a voltage source.
If the voltage source can source positive and negative voltage
and the DUT is a two terminal device such as resistor or diode,
then you can use two voltage source to double the output.
As you can see in the left figure, the voltage across the terminals is double of Vset.
But if you want to force high voltage relative to ground, you can't use this method.
You can double the output voltage by using two voltage source which may float independently.
I'd like to show how to double the output voltage by using B2912A Souce Measure Unit, SMU.
This SMU can force voltage or current and it can force up to +/-210 V and source or sink 105 mA.
B2912A has two channels and each channel may float independently.
By connecting two channels in series, you can double the output voltage up to +/-420 V.
This figure shows how to connect two SMUs in series.
Low force terminal of channel two is connected to chassis ground.
Low force terminal of channel one is set to floating
and this low force is connected to high force terminal of channel two.
Both SMUs are set as a voltage source.
Output voltage of these two channels are set so that the summed voltage would be equal to the applied voltage.
Channel two acts to set the low side voltage of channel one, and it sources the current,
so the current limit must be set so that channel two can source or sink enough current.
Two channels are combined so when you force or measure the voltage, you need to sum both channels.
For the current, read the value of channel one.
10M ohm resistor is connected as a DUT.
You must pay attention when handling the terminals of floated SMU,
since the terminals might be over 200 V.
I'll connect the interlock terminal of the SMU to the test fixture.
By using the interlock function,
hazardous voltages won't be forced when the test fixture lid is open.
Let's measure the voltage and see if the expected voltage is applied.
I'll measure the gurad terminal of channel one by using this Digital Multi Meter.
Both channel one and two is set to 200 V so the summed voltage is 400 V.
As you can see on the DMM, the measured voltage is about 400 V.
Measured current on SMU channel one is about 40 uA which matches the expected value.
This is B2961A Power Source.
I'll use this as a voltage source and measure a three terminal device.
B2961A/62A can also be used as floating voltage source,
but here I'll connect the low force terminal to ground.
Connect low force of channel two to souce terminal,
high force of channel one to drain terminal,
and connect the voltage source to gate terminal.
This is the actual setup to measure a MOS-FET.
I'll use the sweep function of B2912A.
Gate terminal is set to 3 V.
Ouput voltage of channel two is set to 200 V,
and I'll sweep the output voltage of channel one from -200 V to +200 V.
Let's start the measurement.
By this sweep operation, applied voltage to the DUT is from 0 V to 400 V.
You can connect more than two SMUs in series.
For example you can connect five SMUs in series and force 100 V, 1 A.
As showed in this figure, you can expand the setting range.
Low force terminal of B2911/12A may be floated up to +/-250 V relative to chassis ground.
Thank you for watching the video.
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