I'd like to design a simple AM radio receiver. It should be able to drive a small speaker, and the antenna shouldn't have to be longer than a meter.
I plan to use 2 transistors as common-emitter amplifiers, to get a gain around 15000 (and perhaps another transistor or two as emitter followers to increase the current), an LC tuned filter, and a simple diode + low pass filter for detection.
A few questions:
1. Is this enough to drive the speaker? What type of signal do I need to drive a small, inexpensive, stock speaker?
2. What kind of voltage signal can I expect off the antenna? What type of output impedance / current?
3. Should I amplify, then filter; or filter, then amplify; or amplify some, then filter, then amplify more? What are the tradeoffs?
I plan to use 2 transistors as common-emitter amplifiers, to get a gain around 15000 (and perhaps another transistor or two as emitter followers to increase the current), an LC tuned filter, and a simple diode + low pass filter for detection.
A few questions:
1. Is this enough to drive the speaker? What type of signal do I need to drive a small, inexpensive, stock speaker?
2. What kind of voltage signal can I expect off the antenna? What type of output impedance / current?
3. Should I amplify, then filter; or filter, then amplify; or amplify some, then filter, then amplify more? What are the tradeoffs?