BJT Collector to Emitter Leakage Test Report (Am I making any mistakes?)

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dcbingaman

Joined Jun 30, 2021
495
Attached is a report I created today using a 30V DC bench supply. The test setup is intended to measure various BJT leakage currents. I tested with three different transistor types that I happen to have in stock. (These transistors are a little old). The circuit was setup in a solderless breadboard. The BJT's where all TO-92 case styles. The results seemed to amaze me, so wondering if I am making a mistake somewhere. Attached is the testing setup and results.
 

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dl324

Joined Mar 30, 2015
13,492
Whatever leakage current you're trying to measure, you're not doing it right.

Leakage currents are measured near the breakdown voltage. Typically, we measure C-E leakage with the base terminal open (Iceo). You can also measure Icer, Ices, Icev, icex.

In the Onsemi datasheet, they report Icex.

1628719331117.png
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
495
I think you do leakage current with the base open, and sweep Vcc.

View attachment 245414
On the bench I found similar results with base open. I see for these two parts it is still less than 1nA up to 40V. Thanks for the simulation. Can you provide the .asc? Also found you have to wait a long time when the base is open in my test circuit for it to charge the Collector to Base 'capacitance' when I tried this same circuit in LTSpice with base open.

Thanks
 

Papabravo

Joined Feb 24, 2006
17,235
On the bench I found similar results with base open. I see for these two parts it is still less than 1nA up to 40V. Thanks for the simulation. Can you provide the .asc? Also found you have to wait a long time when the base is open in my test circuit for it to charge the Collector to Base 'capacitance' when I tried this same circuit in LTSpice with base open.

Thanks
Sure. Here you go.
 

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Thread Starter

dcbingaman

Joined Jun 30, 2021
495
I think you do leakage current with the base open, and sweep Vcc.

View attachment 245414
I think you do leakage current with the base open, and sweep Vcc.

View attachment 245414
If you are going to sweep the voltage you are going to have to do that really slowly. Considering the Collector to Base Capacitance is around 8pF for a typical low signal level dV/dt say you sweep from 0 to 30V in 10ms. That is 3000V/s with 8pF that is a current of 24nA. Even when you take a second for the sweep the current is still 0.24nA. Which has nothing to do with leakage.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
495
If you are going to sweep the voltage you are going to have to do that really slowly. Considering the Collector to Base Capacitance is around 8pF for a typical low signal level dV/dt say you sweep from 0 to 30V in 10ms. That is 3000V/s with 8pF that is a current of 24nA. Even when you take a second for the sweep the current is still 0.24nA. Which has nothing to do with leakage.
Never mind. I see the 'sweep' as it is defined in LTSpice uses a linear set of steps and assumes steady state for each one.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
495
Whatever leakage current you're trying to measure, you're not doing it right.

Leakage currents are measured near the breakdown voltage. Typically, we measure C-E leakage with the base terminal open (Iceo). You can also measure Icer, Ices, Icev, icex.

In the Onsemi datasheet, they report Icex.

View attachment 245415
I repeated the test at 30V with open base. Though the leakage current was higher at first it came down over a long time (minutes) to about the same as when the base was tied to the emitter via 10K. Theory is there is an emitter to base current that is charging the Collector to Base Capacitance and until that charge is complete the reading is not stable.

30V is the limit for the PN2222 the limit for the other two is 40V but my power supply only goes up to 30V.

Attached is the updated test report that includes three more test (1A,2A and 3A) with the same transistors but open base.
 

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Papabravo

Joined Feb 24, 2006
17,235
Do you have the 2N2222A model? I don't have that one with LTSpice. Thanks.
I have a 2N2222A model. There are many models out there and no authority to rate or evaluate them. This is what I have.

.model 2N2222A NPN(IS=3.88184e-14 BF=929.846 NF=1.10496 VAF=16.5003 IKF=0.019539 ISE=1.0168e-11 NE=1.94752 BR=48.4545 NR=1.07004 VAR=40.538 IKR=0.19539 ISC=1.0168e-11 NC=4 RB=0.1 IRB=0.1 RBM=0.1 RE=0.0001 RC=0.426673 XTB=0.1 XTI=1 EG=1.05 CJE=2.23677e-11 VJE=0.582701 MJE=0.63466 TF=4.06711e-10 XTF=3.92912 VTF=17712.6 ITF=0.4334 CJC=2.23943e-11 VJC=0.576146 MJC=0.632796 XCJC=1 FC=0.170253 CJS=0 VJS=0.75 MJS=0.5 TR=1e-07 PTF=0 KF=0 AF=1)
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
495
I have a 2N2222A model. There are many models out there and no authority to rate or evaluate them. This is what I have.

.model 2N2222A NPN(IS=3.88184e-14 BF=929.846 NF=1.10496 VAF=16.5003 IKF=0.019539 ISE=1.0168e-11 NE=1.94752 BR=48.4545 NR=1.07004 VAR=40.538 IKR=0.19539 ISC=1.0168e-11 NC=4 RB=0.1 IRB=0.1 RBM=0.1 RE=0.0001 RC=0.426673 XTB=0.1 XTI=1 EG=1.05 CJE=2.23677e-11 VJE=0.582701 MJE=0.63466 TF=4.06711e-10 XTF=3.92912 VTF=17712.6 ITF=0.4334 CJC=2.23943e-11 VJC=0.576146 MJC=0.632796 XCJC=1 FC=0.170253 CJS=0 VJS=0.75 MJS=0.5 TR=1e-07 PTF=0 KF=0 AF=1)
I ran your same test with the 2N2222 which is in my library. I got slightly higher leakage currents in the SIM with the 2N2222 model I had, but still under 10nA even up to 40V.
 
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