I need to simulate a simple clamp circuit in ADS using a simple diode having some threshold voltage. I used a diode from the devices-linear library but surprisingly the diode conducts for both negative and positive voltages. Seems like it acts like a short circuit. However there are some nonlinear diode models with many parameters but I do not need to make it so complicated. I only need it to conduct for positive voltages. I was wondering if anyone could help me please?

Thanks in advance