We chose the analog FM transmitter shown below to implement
as our final design.
FM transmitter (88-108 MHz) #5
1.4V supply voltage
11 components: 2 transistors, no tunnel diode
Substituted 2N3904 npn transistors for the 2
transistors in the schematic
Figure 1. Schematic of transmitter circuit
resulted in a clear transmission distance of about 10 feet with
the breadboard prototype shown below
is powered by a 1.4V size 10 hearing aid battery.
Composed of basic resistors, capacitors,
transistors, and an inductor
Components are inexpensive and readily available
Relatively simple to implement
Figure 2. Prototype of the
analog FM transmitter.
Final Printed Circuit Board
Utilizes surface mount components
Width : 11.6
to easily fit within the ear
show approximately 35 hours of battery life with a 1.4V hearing
Figure 3. Final PCB.
Figure 4. Microphone and PCB in an ear mold.