If I, for example, set the voltage of the base of a transistor to 50% duty, will the collecter emitter voltage also be 50% of what it would normally be?

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    \$\begingroup\$ That depends on the frequency and duty cycle of the PWM, what the powre rails are, what the current going into the transistor, the transistor type and model and how you've limited the current with resistors. Need more info, much much more info. \$\endgroup\$ – Voltage Spike Jan 20 '17 at 20:42
  • \$\begingroup\$ The short answer is no: bipolar transistors are current operated, current-output devices. You can use one to amplify a PWM signal but you need more context. \$\endgroup\$ – pjc50 Jan 20 '17 at 20:58
  • \$\begingroup\$ @pjc50 if you can elaborate a bit, please post it as an answer \$\endgroup\$ – Evan Chen Jan 20 '17 at 21:35

< If Arduino analog PWM voltage is put into the base of the transistor, will the collecter emitter voltage also be analog?

all digital signals are analog in that they are some levels of voltage or current.

whether a signal is analog or digital will depend on how such a signal is interpreted. if a 1.1v signal is interpreted differently than a 1.0v signal, that's considered "analog" - where the levels of the signal have meanings.

conversely, if levels of signals are meaningful only if the differences are substantial, that's a digital signal.

fundamentally, that's why a digital signal, or a digital process, is more robust and resistant to noise.

  • \$\begingroup\$ Thank you, you helped me realize I used the incorrect term. I meant to ask whether the PWM duty of the base would limit the voltage of the emitter \$\endgroup\$ – Evan Chen Jan 20 '17 at 21:33
  • \$\begingroup\$ i'm not sure what you meant by that statement above. but if you apply a pwm signal to the base, the collector will have a pwm output, out of phase with the signal on the base. another way to put it, a pwm signal with a duty cycle % on the base will generate a pwm signal on the collector with a 1 - duty cycle %. \$\endgroup\$ – dannyf Jan 20 '17 at 21:35
  • \$\begingroup\$ There are many differential signalling protocols with a voltage swing of less than 200mV, so your statements about analogue and digital are not entirely accurate given that a digital signal of this sort would fit into your description of analogue given that the difference in levels are not "substantial". A digital signal would still be digital even if the levels were 1.0V and 1.1V. \$\endgroup\$ – Tom Carpenter Jan 20 '17 at 21:43
  • \$\begingroup\$ A more accurate definition is that an analogue signal is one which deals with a uncountable range of values (e.g. a pure sinusoidal voltage signal has an infinite number of indiscrete levels). A digital signal is one in which a countable set of values is used to represent information (e.g. a PWM signal). The difference between the levels is somewhat irrelevant as long as they can be individually interpreted into some countable set. \$\endgroup\$ – Tom Carpenter Jan 20 '17 at 21:50
  • \$\begingroup\$ The real world is analog. Digital is an abstraction that allows us to accomplish a variety of tasks more efficiently. \$\endgroup\$ – mkeith Jan 21 '17 at 6:19

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