# BJT Output Characteristics Question

Ok, so I am pretty confused at the moment with a question that I have been given to work out by my lecturer and was wondering if I could get some guidance with it. I will attach images of the question and diagram of the circuit while trying to say how I believe it should be worked out. I have not yet had the classes for this question yet but wanted to get a better understanding of it before I go into the class.

But I guess my main question would be this, is there a calculation that I could use to get a measurement of $$I_b$$ reliably without having to randomly guess numbers to get to 10 micro Amps and with regards to the results I have currently would you say I am on the right track? As I feel like I am complicating the question more than I should be.

So the question says "Using Figure 8 adjust VBB so that the base current is set at 10 micro Amps, and complete table 4."

Straight away I see that $$I_b$$ going to the base of the emitter has to be reading 10 micro Amps, I have a multi meter in place to make sure it is the reading I am getting but to do this I have to change the VBB voltage to make the multi meter read the right amount of Amps. So for me I have literally been spending 5 minutes trying to find out what 10 micro Amps is every time and id assume there is a much easier way to find this than spending 5 minutes doing 0.556677, 0.556679, 0.556683 etc until I find the right value.

I had also took note that I am given VCE which tells me if I change VCC to say 0.6V I will get the same reading on the VCE meter of 600mV and I have to work out $$I_c$$ which is the measurement on the multi meter from the transistor collector to VCC.

For some reason the attaching a imgur link wont work through the link section so I will leave the link below for the gallery of the 4 images.

Image 1

Image 2

https://imgur.com/gallery/6PdgPZo

• You adjust VBB to get IB to 10uA (XMM1 as an ammeter), then adjust VCC to get VCE (XMM3 as a voltmeter) and measure current IC (XMM2 as an ammeter). Apr 19 '20 at 3:55

Below is the equation for $$I_c$$

$$I_c=\beta I_b$$

$$\beta$$ is unique for the transistor. The value can be found in the transistor datasheet BC107B

In datasheet the parameter $$\beta$$ is usually labeled as $$h_{FE}$$

The $$\beta$$ value for BC107B from the datasheet is

In short you are creating a graph similar to the image below for the BC107B transistor

References: