Hi Experts,
Our customer needs the power consumption, and input resistance for the LM747J/883.
I see power dissipation of 800mW stated in the datasheet. Should I consider this equal to power consumption?
Please also share input resistance as requested. Thank you.
Best regards,
Gerald
Hello Gerald,
So the power dissipation listed in the datasheet is the maximum possible power dissipation. Your power consumption of the device has two components. There is the quiescent current and the output current. Your power will be your current consumed multiplied by your total supply voltage.
The quiescent current of the device is minimum possible power consumption, and the minimum amount of current needed for the amplifier to turn on. This is in the datasheet as Icc, and the maximum values of Icc are listed at room temp, hot temp, and cold temp.
Your max quiescent current is 6.6mA, at +/-22V that is a maximum base power dissipation of 290.4mW
Your output current is going to be decided by your output voltage and load. If you are trying to output 10V on a 1k resistor, your output current is going to be 10mA. 10mA at +/-22V is 220mW, which will be added to your max base of 290.4mW.
Your input resistance is the resistance looking into the base of a BJT. You can estimate this by dividing the input common mode voltage by your input bias current. At 12V your max input bias current is 1500nA. 12V/1500nA = 8 megaohms as your worst case impedance.
Best,
Jerry
