wanna_eat_1kg_of_elecons
New Member
Hello,
I hope you can help me out. I made this circuit with a pair of BC337 transistors:
**broken link removed**
I am getting strange results so first i will describe what i did and then i'll ask my questions
I made a current source and measured the current @ 2mA that was what i calculated so that part went fine.
Then i calculated the bias point. Vcc is 6.2V and there is 2 mA for both RC resistors so one resistor gets 1mA. The resistor i choose was 2k7 so the bias point is Vcc - (2k7 * 1mA) = 3V5
Then i calculated the gain. As G_diff = Rc/2*(re + RE) --> 2700/2*(25 + 100) = 10.8
(Question 1)
So i expect that if one base is 100mV higher than the other base the output will be Gain * 100mV + bias_voltage. So if i make one base 100 mV higher than the other one i suspect 3.5V + 1.08V = 4.58V
Is this assumption correct?
so i did put one base at 3.5v and added Delta V to the other base with a PSU the values i measured are:
Delta (mV) ------ Output
0 ------- 3.29v
100 ------- 4.1v
200 ------ 4.77v
300 ------ 5.54v
if i calculate it like this for delta = 300mV:
5.54 - V_bias = 5.54 -3.5 = 2.04
Gain is Output/ input ---> 2.04/300mV = 6.8
(Question 2)
Did i calculate the gain wrong? I Calculated 10.8 and measured a gain of 6.8
I want to use this amplifier to multiply a small delta voltage. But the common between 4 and 2.5 volt so. If i put 2.5v on one base and 2.6v on the other. Or 4v on one base and 4.1 volt on the other. I want an output of bias + gain * delta_v = 3.5 + 1.08 = 4.58
Question 3
Can i do it with this circuit?
Question 4
When i measure the other Collector it is always about 3V except for the case when delta = 0 then it is 3.6V. It looks like it is clipping what am i doing wrong i think i am missing the point here and i am running in circles.
Can someone please help me out?
I know op amps are easier but i want to learn transistors so please no opamp remarks.. (maybe i'll try them in a few wile but for now it is transistors)
i am tired now so i hope my text makes sense thanks for the effort !!
I hope you can help me out. I made this circuit with a pair of BC337 transistors:
**broken link removed**
I am getting strange results so first i will describe what i did and then i'll ask my questions
I made a current source and measured the current @ 2mA that was what i calculated so that part went fine.
Then i calculated the bias point. Vcc is 6.2V and there is 2 mA for both RC resistors so one resistor gets 1mA. The resistor i choose was 2k7 so the bias point is Vcc - (2k7 * 1mA) = 3V5
Then i calculated the gain. As G_diff = Rc/2*(re + RE) --> 2700/2*(25 + 100) = 10.8
(Question 1)
So i expect that if one base is 100mV higher than the other base the output will be Gain * 100mV + bias_voltage. So if i make one base 100 mV higher than the other one i suspect 3.5V + 1.08V = 4.58V
Is this assumption correct?
so i did put one base at 3.5v and added Delta V to the other base with a PSU the values i measured are:
Delta (mV) ------ Output
0 ------- 3.29v
100 ------- 4.1v
200 ------ 4.77v
300 ------ 5.54v
if i calculate it like this for delta = 300mV:
5.54 - V_bias = 5.54 -3.5 = 2.04
Gain is Output/ input ---> 2.04/300mV = 6.8
(Question 2)
Did i calculate the gain wrong? I Calculated 10.8 and measured a gain of 6.8
I want to use this amplifier to multiply a small delta voltage. But the common between 4 and 2.5 volt so. If i put 2.5v on one base and 2.6v on the other. Or 4v on one base and 4.1 volt on the other. I want an output of bias + gain * delta_v = 3.5 + 1.08 = 4.58
Question 3
Can i do it with this circuit?
Question 4
When i measure the other Collector it is always about 3V except for the case when delta = 0 then it is 3.6V. It looks like it is clipping what am i doing wrong i think i am missing the point here and i am running in circles.
Can someone please help me out?
I know op amps are easier but i want to learn transistors so please no opamp remarks.. (maybe i'll try them in a few wile but for now it is transistors)
i am tired now so i hope my text makes sense thanks for the effort !!