BF245 transistor

BF245 transistor
BF245 transistor

BF245 is a JEFT n-channel transistor, it is a VHF/UHF amplifier transistor, this is why the popularity of this JEFT is not over at modern electronic circuits, in this article we explain all specifications about BF245 transistor.

Electrical specification & features of BF245 JFET   

  • BF245 is an N-channel JFET transistor
  • Drain to source voltage (VDS) is +/-30V
  • Drain to gate voltage (VDG) is 30V
  • Gate to source voltage (VGS) is 30V
  • Gate to source (VGS) is 4 to 7.5V
  • Gate to source cutoff voltage (V­­GS (OFF)) is -8.0V
  • Drain current (ID) is 100mA
  • Forward gate current (IG (F)) is 10mA
  • Zero-gate-voltage-drain current (IDSS) is 2 to 25mA
  • Power dissipation (PD) is 350mW
  • Maximum Temperature is -65 to +150°C
  • Cutoff frequency (F (Yfs)) is 700MHz



The PINOUT configuration of the BF245 transistor is SGD and the package used is TO-92, it is a common PINOUT pattern and package for a transistor, the TO-92 package is very useful for compactness.

SMD version of BF245 JFET

The BF545 is the SMD version JFET transistor for BF245, the BF545 transistor had applications at modern electronic circuits as UHF/VHF amplifiers.

The electrical specifications of BF545 and BF245 are almost the same, the characteristics like power dissipation and frequency are different.

SMD version JFET transistor package

The BF545 SMD version JFET transistor had a SOT-23 package, the PINOUT pattern is entirely different at this version.

Electrical characteristics & application description of BF245 JEFET transistor

Voltage characteristic

Drain to source voltage, drain to gate voltage and gate to source voltage of BF245 transistor is 30V, this is why it is called a low power amplification component.

The gate voltage is 0.4v to 7.5v and the gate to source cutoff voltage is -8.0v, both these values are very much associated with the switching operation of the BF245 JFET transistor.

Current characteristic

The drain current is 100mA, it is the maximum load value of this JFET and the forward gate current is 10mA, which is the peak current value need to trigger.

The Zero-gate-voltage-drain current is 0.2 to 25mA, it is the current flows when the gate voltage is zero.

Small-signal applications the DC gain is much higher up to 350 to 1400hFE. 

Cutoff frequency

The cutoff frequency at BF245 JFET is 700MHz, it is a filter to maintain a frequency value.

Dissipation & temperature capacity

The power dissipation of the BF245 JFET transistor is 350Mw, it is the maximum power consumption capacity of this transistor.

The operating or storage temperature value of the BF245 transistor is -65 to +150°C, it is the heat capacity of this device.

Uses of BF245 JFET

  • UHF frequency amplifier
  • VHF frequency amplifier
  • RF oscillator
  • RF amplifier circuits
  • Audio amplifier
  • Small signal amplifier

BF245 JFET transistor equivalent

The transistors like BF245C, 2SK117, MPF102, 2N5458, NTE457, are the perfect equivalent of the BF245 JFET transistor.

Each transistor on this list had almost the same specification as the BF245 transistor, but on a replacement process, you need to check the specs become selecting.

BF245 vs 2n5457 

Drain to source voltage (VDS)+/-30V25V30V
Drain to gate voltage (VDG)30V25V30V
Gate to source voltage (VGS)30V-30V
Drain current (IG)100mA10mA-
Power dissipation350mW310mW360mW
Forward gate current (IG (F))10mA-10mA
Cut-off frequency (F(Yfs))700MHz-1000MHz
Gate to source cut-off voltage (VGS (OFF))-8.0V-0.5 to -6.0V-
Zero-source voltage-drain current (IDSS)2 to 25mA1 to 9mA7mA

Both three transistors such as BF245 vs 2N5457 vs BF256 had almost the same electrical specifications.

When we looking at the ability of these transistors separately, the BF256 had more ability to handle UHF/VHF signal applications.

Guitar preamp circuit based on BF245 JFET

Guitar preamp circuit based on BF245 JFET
Guitar preamp circuit based on BF245 JFET

The circuit shows the preamplifier using BF245 JFET as the main component and we can also replace BF245 with BF256.

When the audio signal reaches the transistor, it amplifies the signal and passes it over to the main amplifier stage.

Datasheet in pdf

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