electronoobz
- Jan 14, 2012
- 226
- Joined
- Jan 14, 2012
- Messages
- 226
According to http://www.williamson-labs.com/480_xtor.htm
Since the Transistor is a Current device, any signal Voltage must first be
Converted to a Current.
Voltage to Current Convertor
First, you must convert the input voltage to a current by
using a Voltage to Current Convertor--a resistor.
Next,
Since the Transistor is a Current in/Current out device, any Current Output is
Converted to a Voltage Drop by the Current flowing thru a Load Resistor.
Current to Voltage Convertor
Next, you convert the output current into a voltage by
using a Current to Voltage Convertor in the collector circuit--
you guessed it--a resistor
Abstractly, here are some Characteristics: 1. An equivalent circuit of a NPN transistor is two diodes tied anode to anode; one cathode being the emitter, the other the collector, and the junction of the anodes is the base. 2. When a NPN transistor is doing-its-thing, there is always a constant 0.6 volt drop between the base and emitter, i.e., the base is always ~ 0.6 volts more positive than the emitter--always! 3. There is no output at the collector, until the base has reached ~ 0.6 volts and the base is drawing current, i.e., any signal that appears at the base that is not up to ~ 0.6 volts (and not drawing base
current), is never seen at the collector. 4. The base requires a current, not a voltage to control the collector current. 5. The collector is a current source: it does not source a voltage. 6. The collector appears to output a voltage when a resistor is connected between it and power. 7. The collector is a high impedance when compared to the emitter. 8. The transistor can output an amplified signal either from the collector or the emitter (or both). 9. When operating with a collector resistor (RL): the output voltage from the collector is an amplified voltage. 10. When operating with only an emitter resistor (Re): the output voltage from the emitter is not an amplified voltage, because it is always ~ 0.6 volts, below the input (base) voltage--hence the name
voltage follower. But because the emitter can source large amounts of current to the "LOAD," it can be said, there was CURRENT amplification. 11. The collector--being high impedance--cannot drive a low impedance load. 12. The emitter--being a low impedance--can drive a low impedance load. 13. The voltage gain from the collector is greater than one (Gv > 1). 14. The voltage gain from the emitter is less than one (Gv < 1). 15. Both the collector and the emitter: output ~ the same power: E x I = P.
Since the Transistor is a Current device, any signal Voltage must first be
Converted to a Current.
Voltage to Current Convertor
First, you must convert the input voltage to a current by
using a Voltage to Current Convertor--a resistor.
Next,
Since the Transistor is a Current in/Current out device, any Current Output is
Converted to a Voltage Drop by the Current flowing thru a Load Resistor.
Current to Voltage Convertor
Next, you convert the output current into a voltage by
using a Current to Voltage Convertor in the collector circuit--
you guessed it--a resistor
Abstractly, here are some Characteristics: 1. An equivalent circuit of a NPN transistor is two diodes tied anode to anode; one cathode being the emitter, the other the collector, and the junction of the anodes is the base. 2. When a NPN transistor is doing-its-thing, there is always a constant 0.6 volt drop between the base and emitter, i.e., the base is always ~ 0.6 volts more positive than the emitter--always! 3. There is no output at the collector, until the base has reached ~ 0.6 volts and the base is drawing current, i.e., any signal that appears at the base that is not up to ~ 0.6 volts (and not drawing base
current), is never seen at the collector. 4. The base requires a current, not a voltage to control the collector current. 5. The collector is a current source: it does not source a voltage. 6. The collector appears to output a voltage when a resistor is connected between it and power. 7. The collector is a high impedance when compared to the emitter. 8. The transistor can output an amplified signal either from the collector or the emitter (or both). 9. When operating with a collector resistor (RL): the output voltage from the collector is an amplified voltage. 10. When operating with only an emitter resistor (Re): the output voltage from the emitter is not an amplified voltage, because it is always ~ 0.6 volts, below the input (base) voltage--hence the name
voltage follower. But because the emitter can source large amounts of current to the "LOAD," it can be said, there was CURRENT amplification. 11. The collector--being high impedance--cannot drive a low impedance load. 12. The emitter--being a low impedance--can drive a low impedance load. 13. The voltage gain from the collector is greater than one (Gv > 1). 14. The voltage gain from the emitter is less than one (Gv < 1). 15. Both the collector and the emitter: output ~ the same power: E x I = P.
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