# Voltage*time product of pulse transformer

I am designing a circuit to excite a piezo-electric crystal with 1MHz bipolar square wave at 30V (Vp-p=30V, Vb-p=15V) consisting of 10 pulses, 50% duty cycle.

The idea is to use a pulse transformer whose inputs shall be driven with +15V from either directions to achieve bipolar excitation. First, IN_A will be driven with +15V while IN_B is at ground and vice versa.

1) The voltage * time product in this case should be 15V * (1/1MHz) = 15V-us. Is this correct?

2) Or should it be 30V * (1/1MHz) = 30V-us since the excitation is bipolar?

3) Finally, since the excitation consists of 10 pulses and not just a single pulse, should the calculation of V * t value take that into account as well?

• How do you reset the core? Commented Jul 3, 2018 at 7:49
• @winny OP says the driving is done +15 on IN_A, with IN_B grounded, then IN_A grounded and IN_B with +15, which is zero average. Commented Jul 3, 2018 at 9:44
• @aconcernedcitizen Sure, but without some servo feedback for adjusting the duty cycle or the individual rails, it will never fully cancel out each other. Commented Jul 3, 2018 at 9:59
• @winny That's also true, if OP doesn't keep his 50% duty-ratio true. Commented Jul 3, 2018 at 13:46
• @aconceredcitizen That, or missmatch between the rails. In practice, both. Commented Jul 3, 2018 at 13:58