# 90 degree phase shift?

by morten84
Tags: degree, phase, shift
 P: 87 OK, the answer is simple. Do you need lag/leading network? There are four typical topologies that are used to lag/lead a signal: T,Pi networks with passive components. T-network, Lag: Here is spice code for the network R1 1 2 100 C 2 0 1u R2 2 3 100 T-network, Lead: C1 1 2 1u R1 2 0 100 C2 2 3 1u Pi-network, Lead C1 1 0 1u R1 1 2 100 C2 2 0 1u Pi-network, Lag R1 1 0 100 C1 1 2 1u R2 2 0 100 NB. values in the spice code are just arbitrary. You just need to derive the transfer function for the network of interest, in $$j\omega$$ terms and find the equation that defines phase shift (something with $$tan^{-1}()$$), so you'll basically need to work your way back. Just remember that those networks will also transform input/output impedance of your circuit and be sure to identify the frequency bandwidth of your accelerometer, so your phase lead/lag network won't interfere with the sensor. BTW, that's the first time I've heard of need to shift the signal in order to get the accelerometer to function properly, I've worked with them before and have not experienced any problems with lagging. Probably because of the integrator. P.S Are you Norwegian?