AC128 transistor

AC128 transistor
AC128 transistor

AC128 transistor specification

  • AC128 is a germanium PNP type transistor
  • Collector to emitter voltage is 32V
  • Collector to base voltage is 32V
  • Emitter to base voltage is 10V
  • Collector current is 1A
  • Power dissipation is 700mW
  • DC current gain is 55 to 175hFE
  • Transition frequency (FT) 1MHz
  • Junction temperature is between –55 to +75

AC128 transistor Pinout

AC128 transistor Pinout
AC128 transistor Pinout
Pin Number Pin Name Description
1 EMITTER The emitter is the input of the transistor.
2 BASE The base is used to trigger the transistor 
3 COLLECTOR The collector is the output of the transistor


AC128 transistor package

The component package used for the AC128 transistor is TO-1, it is an old type transistor package mainly used for amplifier transistors.

The TO-1 is made with an outer metal cover and they had a circle shape, they are been mainly used for old audio applications.

AC128 transistor specification and application description

In this section, we try to explain the electrical specifications of the AC128 transistor, this helps explain the application description.

Voltage specs

The voltage specs of AC128 transistor are collector to base voltage is 32V, collector to emitter voltage is 32v and emitter to base voltage is 10V, the voltage specs show that AC128 is a transistor used for audio applications.

Current specs

The collector current is 1A, the current values are moderate as a transistor device.

Dissipation specs

The power dissipation of the AC128 transistor is 700mW, the TO-1 transistor package had a great influence on the power dissipation.

Current gain specs

The current gain of the AC128 transistor is 55 to 175hFE, the amplification capability of this transistor is high, this is due to they are outdated model germanium semiconductor transistor devices.

Transition frequency

The transition frequency is 1MHz, the frequency limit of the AC128 transistor is higher.

Junction temperature

The junction temperature of -55 to +75℃, the germanium material-based device had a lower temperature capacity than silicon material.

AC128 transistor Datasheet

AC128 transistor Datasheet
AC128 transistor Datasheet

If you need the datasheet in pdf please click this link

AC128 transistor equivalent

The transistor such as 2n2905, 2n4032, 2n3109, bc337, NKT275, and bc108 are the equivalent for AC128 transistors.

The electrical specs and physical characteristics of all the transistors are the same, so we can easily replace them with an AC128 transistor.

AC128 complementary transistor

The AC127 transistor is the complementary transistor for the AC128 transistor, both of them are combined to form many audio-based applications.

AC128 vs 2N2905 vs BC337

The comparison table explains to you about electrical specifications of AC128 vs 2N2905 vs BC337, this will us an idea about each of these transistors.

Characteristics   AC1282N2905BC337
Collector to base voltage (VCB)32V60V50V
Collector to emitter voltage (VCE)32V40V45V
Emitter to base voltage (VEB)10V5V5V
Collector current (IC)700mA0.6A800mA
Power dissipation700mW0.8W625mW
Junction temperature (TJ)-55 to 75°C-65 to +200℃-55 to 150°C
Transition frequency (FT)1MHZ200MHZ210MHz
     Noise (N)---
   Gain (hFE)55 to 175hFE20 to 75hFE100 to 630hFE

The electrical specification of each of this three AC128, 2N2905, and BC337 are the same, but AC128 is the transistor made with germanium material but 2n2905 and BC337 will be made with silicon material.

Due to silicon and germanium material contradiction, the temperature and packaging are way different.

Applications of AC128 transistor

  • Old AM radio system
  • Old television system
  • Fuzz face circuit
  • Audio system

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