If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

# LM324A Amplifier VOH voltage change @different temperatures

Other Parts Discussed in Thread: LM324A

Hi,

I am doing some calculations with the LM324A OpAMP and was wondering if you could provide me with some additional info, mainly, what is the maximum voltage drop for "High-level output voltage (VOH)" at different temperatures (e.g. in full range) and also under different loads? In the datasheet (page 6, rev jan 2014) it is specified as "VCC-1.5V" but only at Ta=25°C and RL=2kOhm. The VCC in my appllication is 5V.

Thank you for the informations and have a nice day.

Best regards,

M.Gostencnik

• Gostencnik,

Expect VOH to be 3.5V + 4mV * (TJ - 25C) for temperature effect.
As output current approaches current limit VOH will fall another 600 mV.
There is little VOH increase for loads lighter than 2k.
• Michallick,

Based on this information then the VOH is:

@TA=0°C: 3.5V+4mV * (0C - 25C)= 3.4V

@TA=60°C: 3.5V+4mV * (60C - 25C)= 3.64V

Offourse, if I assume that the TJ = TA. However, is the "4mV" you used a fixed constant and where did you get this information?

Ron Michallick said:
As output current approaches current limit VOH will fall another 600 mV.

Can I threat it as a linear (0mA/0mV & -60mA/600mV)? Does this apply for the source or sink currents?

Best Regards,

M.Gostencnik

• Gostencnik,

4mV is double 2mV for two VBE drops. It come from the forward voltage of a silicon diode that has a temperature coefficient of almost exactly -2mV/C.

It linear at high currents and logarithmic at very low current. Linear is good enough approximation.

Sink current is very much different. A picture will help here.