zener voltage การใช้

• Partial damage of the junction can shift its Zener voltage.
• The constant Zener voltage is applied across the base of Q1 and emitter resistor, R2.
• As a result, the current flowing through the load is constant as well; it is exactly the Zener voltage divided by the sense resistor.
• A Zener diode exhibits almost the same properties, except the device is specially designed so as to have a reduced breakdown voltage, the so-called Zener voltage.
• The voltage at the gate terminal will be pulled down to V Z ( the zener voltage ), exceeding the gate trigger voltage of the TRIAC and latching it on.
• The regulation of this circuit is also not very good because the Zener current ( and hence the Zener voltage ) will vary depending on V _ \ mathrm { S } and inversely depending on the load current.
• This circuit has much better regulation than the simple shunt regulator, since the base current of the transistor forms a very light load on the Zener, thereby minimising variation in Zener voltage due to variation in the load.
• Like a typical diode, there is a fixed anode and cathode in a Zener diode, but it will conduct current in the reverse direction ( electrons flow from anode to cathode ) if its breakdown voltage or " Zener voltage " is exceeded.
• In this bipolar junction transistor ( BJT ) implementation ( Figure 4 ) of the general idea above, a " Zener voltage stabilizer " ( R1 and DZ1 ) drives an " emitter follower " ( Q1 ) loaded by a " constant emitter resistor " ( R2 ) sensing the load current.