My Lightbulb is not Lighting Up

[Jonson_2]

Hello, I have created a Photodiode with an op amp with it. The voltage reached 12 volts because of the op amp but the Lightbulb is not working. Please help me. I need the lightbulb to light up when it reached its maximum voltage which is 12V. 

Here is the link for my work on MultisimLive: https://www.multisim.com/content/hbj569G336ni6BfNBZ9TLE/testing-ground-part-2/open/

[VA.KI]

Hello,

You put amplification too much and on the output, you were getting ~100V. This blows up the light bulb.

I've found a good value for resistor R2 = 26k Ohm and it works well.

[GGoodwin]

Hi Jonson_2 and VA.KI,

VA.KI suggests to decrease the gain so that the output voltage will not exceed the burnout voltage of the lamp. Multisim / Multisim Live simulates a fault for the lamp, exceeding the burnout voltage destroys the filament causing the lamp to become open for the rest of simulation.

An inherent voltage limitation can be obtained by using a 5-Terminal, instead of 3-Terminal, Operational Amplifier. In the modified circuit below the op amp is powered from 12 V voltage sources, this protects the lamp against burnout,

A positive voltage can be delivered to the lamp by reversing the current source.

A multitude of Multisim / Multisim Live users don't pay attention to the electrical characteristics of the lamp, they simply connect it to the output of op amps, comparators, 555 Timer, logic gates, etc. We need to note that the lamp conducts quite a large current, especially when driven close to its rated voltage. In the image above the op amp output voltage (which is the lamp voltage) is close to Vee and the current through the lamp is close to 800 mA. These were attained because I modified two parameters of the op amp:

• the Output short-circuit current (Isc) was increased from 25 mA to 2500 mA (2.5 A)
• the Output resistance (Ro) was decreased from 10 Ω to 1 Ω

These modifications can be seen in this screenshot of the Configuration Pane

If Isc is not increased, the current to the lamp will be too low. If Ro is not decreased, the op amp will have larger internal voltage drop causing the lamp voltage to get lower.

VA.KI and I just tried to make the circuit work, at least in simulation. When interfacing photodiode and op amp, however, a circuit based on Inverting Transresistance Amplifier / Current-Controlled Voltage Source could be a better option.

Best regards,

G. Goodwin