IC temperature sensor (Help)

Thread Starter

Alec Laflamme

Joined Dec 21, 2017
Hi, so I'm trying to wrap my head around a problem I've been given to solve. I've inserted the question as a PNG. So I'm very close to getting the provided solution however when I attempt it I get a negative 120 uV/K. My thinking is that if Q1 is connected to the positive terminal of the amplifier and Q2 to the negative then the equation should be as stated Vbe1 - Vbe2. However since Q2 is 4Ic and Q1 is IC, upon simplifying the equation I always end up with kt/q * ln(1/4). This makes my answer negative. Is there something simple I'm missing, or is it possible the given solution is incorrect?