zener diode usage in a reference schematic circuit

I have a circuit that is used for manipulating solenoids. Basically I need help understanding the portion of the circuit C11,D8 and R19.

I also need help understanding C10, R14 and D7.

Why is D7 being used in reverse bias? Does a zener diode that operates in forward bias have the same i-v characteristics of a regular diode?

Hi,
These diodes you referred are not Zener Diodes. These are New Generation Power Diodes (Super Barrier Rectifier). They have an edge on Shottky Diodes in low voltage usage.
Here your referred circuits working as snubber network. If you see the Solenoids are fed positive supply voltage directly and the controlling FETS are making ground circuit, so for bypassing any transient due to inductive load this circuit is used.
If you want information on SBRs here is the link for a better understanding.

http://digitalcommons.calpoly.edu/cg...20rectifier%22

Hope it helps.

To understand the basic circuit function, you can consider the parts simply as regular diodes. For a detail analysis, you would need to know the coil R and L numbers. In a short, the circuit is intended to absorb inductive overvoltages. A simple freewheeling diode is apparently not suffcient, most likely releasing the coil too slow.