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2 change the circuit for better performance
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If you pass 5.5mA from a 1K ohm load, then Vout is 5.5mA * 1K =5.5volt, and circuit saturate before reaching this load.

your circuit works with 5 volt supply and Vcc = R1 * 5.5mA + V_ce + R2 * 5.5mA

for 5.5mA output and RL=20K, you need a supply voltage 20K*5.5mA+..+..> 100V

You need a supply voltage bigger than 100V, No opamp can handle this voltage and this circuit not works a for 20k load.

You can use this circuit instead: refference: http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

opamp power is 5V,

Resense = 100500 ohm

for 5.5 mA output -> vin(VDC) 02.5575 volt

VCC = 20k * 5.5ma + 100500 * 5.5ma + V_CE ~ 120 volt is ok and Q1 should handle 100 volt (minimum (120-110112.5575) volt!)

If you pass 5.5mA from a 1K ohm load, then Vout is 5.5mA * 1K =5.5volt, and circuit saturate before reaching this load.

your circuit works with 5 volt supply and Vcc = R1 * 5.5mA + V_ce + R2 * 5.5mA

for 5.5mA output and RL=20K, you need a supply voltage 20K*5.5mA+..+..> 100V

You need a supply voltage bigger than 100V, No opamp can handle this voltage and this circuit not works a for 20k load.

You can use this circuit instead: refference: http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

opamp power is 5V,

Resense = 100 ohm

for 5.5 mA output -> vin(VDC) 0.55 volt

VCC = 20k * 5.5ma + 100 * 5.5ma + V_CE ~ 120 volt is ok and Q1 should handle 100 volt (minimum (120-110.55) volt!)

If you pass 5.5mA from a 1K ohm load, then Vout is 5.5mA * 1K =5.5volt, and circuit saturate before reaching this load.

your circuit works with 5 volt supply and Vcc = R1 * 5.5mA + V_ce + R2 * 5.5mA

for 5.5mA output and RL=20K, you need a supply voltage 20K*5.5mA+..+..> 100V

You need a supply voltage bigger than 100V, No opamp can handle this voltage and this circuit not works a for 20k load.

You can use this circuit instead: refference: http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

opamp power is 5V,

Resense = 500 ohm

for 5.5 mA output -> vin(VDC) 2.75 volt

VCC = 20k * 5.5ma + 500 * 5.5ma + V_CE ~ 120 volt is ok and Q1 should handle 100 volt (minimum (120-112.75) volt!)

1
source | link

If you pass 5.5mA from a 1K ohm load, then Vout is 5.5mA * 1K =5.5volt, and circuit saturate before reaching this load.

your circuit works with 5 volt supply and Vcc = R1 * 5.5mA + V_ce + R2 * 5.5mA

for 5.5mA output and RL=20K, you need a supply voltage 20K*5.5mA+..+..> 100V

You need a supply voltage bigger than 100V, No opamp can handle this voltage and this circuit not works a for 20k load.

You can use this circuit instead: refference: http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

http://www.ecircuitcenter.com/Circuits/curr_src1/curr_src1.htm

opamp power is 5V,

Resense = 100 ohm

for 5.5 mA output -> vin(VDC) 0.55 volt

VCC = 20k * 5.5ma + 100 * 5.5ma + V_CE ~ 120 volt is ok and Q1 should handle 100 volt (minimum (120-110.55) volt!)