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What is the solution(s) to this question? Maximum points available. Thanks! Texa

ID: 2988163 • Letter: W

Question

What is the solution(s) to this question? Maximum points available. Thanks!

Texas Instruments OPA2134 op-amp datasheet: http://www.ti.com/lit/ds/symlink/opa134.pdf

OPA2134 on TI site: http://www.ti.com/product/opa2134

Find junction temperature of the Texas Instruments OPA2134PA op-amp chip when powered-on but not driving a load (V out A,B = 0). Assume power supply voltages of 15 V, ambient temperature T4 = 30 degree C, and the system has reached thermal equilibrium with no heat sink attached. This particular model has two amplifiers on the chip and uses an 8-pin DIP package. First find the total power supplied to the entire packaged unit. Clearly state the origin of your numbers, and your calculation procedure. Failure to do so is an invitation to receive less points.

Explanation / Answer

In the datasheet in the PowerSupply speifications we have

Operating Voltage =+/-15 V (differential voltage)

Quiscent current per amplifier (by definition current drawn by the amplifier when it is not aplifying and with no load) I = 4 mA

(These are the typlical values. )

Thus the power consumed per amplifier with no load is P=U*I =(15+15)*0.004 =0.12 W

Power for 2 amplifiers is P =2*0.9 =0.24 W

The thermal resistance for 8 pin-DIP package (from datasheet) si

R =100 (deg Celsius/ W)

By definition R = delta(T)/P so the temperature difference between the ambient and the junction is

delta(T) = P*R =0.24*100 =24 degree C

For an ambient temparature of let 30 degree C (86 F) the temperature of the junction will be

Tj =24+30 =54 degree Celsius

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