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BT66T Melody Generator

[Click the image to enlarge it]

BT66T Pin Configuration

Pin No.

Pin Name



Ground (Vss)

Connected to the ground of Circuit


Positive (vdd)

Powers the IC, typically with 3.3V


Output (BD)

This is the output pin, where tone is generated



  • Play a melody consisting of 64 Notes
  • Lower range of operating voltage form 0.3V to 3.5V
  • Typical Operating Voltage: 3.3V
  • Can easily drive a speaker through NPN Transistor
  • Has five different IC to play five different tones
  • Package: TO-92

Note: Complete Technical Details can be found at the datasheet given at the end of this page.


BT66T Equivalent Melody Generator ICs

BT66, UM66


How to select a BT66T for your melody

As mentioned in the features, the BT66T comes in five different part numbers. Each part number has the capability to play a different type of tone. The part number and its respective tone is mentioned in the table below, you can Google the tone name to listen to the type of tone the IC will play.


IC  Part Number

Tone name



For Elise



Jingle Bell



Happy Birthday



Love Story



It’s a Small World


Do remember that this IC will be able to play only one tone, if you need a different tone you have to use a different IC with a different part number as shown above


How to use a BT66T

The BT66T is an easy to use 3 terminal Melody generator IC. It is mainly used in circuits where a tone has to be played as a notification for the user. This IC is easy to use because it can work on low voltage (0.3V to 3.5V) and consumes very little current (1uA) during operation. It can also be easily interfaced with a normal Piezo electric speaker (even buzzer) or to a 6 ohm speaker through a NPN transistor as shown below.

BT66T Circuit

The BT66T can operate only below voltage range 3.5V, so we use a 3.3V Zener Diode to regulate this voltage across the positive (pin 2) of the IC. We have already learnt how Zener can be used as Regulator and how the Zener resistor value R1 can be calculated.

The output of the IC that is the melody can be obtained at the pin BD (pin3). But this pin will not be able to source enough current to drive a speaker (6/8 ohm speaker). So we use a NPN transistor like BC547 to run the speakers. Basically, the output pin (pin 3) turns on and off in a particular fashion to provide the tone. We connect this output to the Base of BC547 which will also switch on and off in the same tone. The speaker is connected in series with the transistor so that the tone can be played in the speaker.


Applications of BT66T

  • Used to play melody
  • Make project more attractive using sound
  • Notify users through a melody
  • Used in Toys, Calling Bells, Alarms etc...


2D representation (TO-92)

BT66T Dimensions

Component Datasheet