2SK170 JFET transistor

2SK170 JFET transistor
2SK170 JFET transistor

2SK170 specs

  • 2SK170 is an N-channel junction type field effect transistor JFET device
  • Gate to drain voltage (VGD) is –40V
  • Gate to source cutoff voltage (VGS (OFF)) is -0.2 to -1.5V
  • Gate to drain breakdown voltage (V (BR) GDS) is -40V
  • Drain gate forward current (IGF) is 10mA
  • Power dissipation (PD) is 400mW
  • Input capacitance (Ciss) is 30pF
  • Junction temperature (TJ) is between -55 to 125℃
  • Noise figure (NF) is 1 to 10dB
  • Low noise audio amplifier application


Pin Number Pin Name Description
1 Drain   The drain terminal is the current inlet of the JFET device
2 Gate The gate is used to trigger the JFET device
3 Source In the source, terminal current flows out from the JFET 


2SK170 package

2SK170 JFET transistor device has a TO-92 device package, it is a general-purpose amplifier and low-power circuit device.

TO-92 is a three-terminal device made of epoxy/plastic material, it will provide compactness and temperature capacity of the component.

The less weight and compactness of the TO-92 package are used to build a project-based circuit.

2SK170 electrical specification and application description

In this explanation we descript the electrical specifications of the 2SK170 JFET device, this will support us in a better understanding of the device and it will very useful in the replacement process.

Voltage specs

The voltage specs of the 2SK170 JFET transistor are the gate-to-drain voltage is -40V and gate-to-source cutoff voltage is -0.2V to -1.5V, the voltage specifications indicate it is an amplifier application device.

Current specs

The gate forward current value of 2SK170 JFET is 10mA, the current value indicates the maximum load capacity of the device.

Dissipation specs

The power dissipation value of 2SK170 JFET is 400mW, the dissipation capacity of the device is mainly depended on the device package.

Junction temperature/operating temperature

The junction temperature/storage temperature of 2SK170 JFET is55 to +125℃.

Input capacitance

The input capacitance value of 2SK170 JFET is 30pF, the capacitance value is important in some applications.

Noise figure

The noise figure value of 2SK170 JFET is 1 to 10Db, this is a wide-range noise value for an amplifier device.


If you need the datasheet in pdf please click this link


The JFET devices such as PN4091, 2SK187, 2SK363, 2SJ108, 2SK1005, 2SK1000, 2SK0615 and 2SK370 are the equivalent devices of 2SK170 JFET. Each of the devices has the same set of electrical specifications.

2SK170 vs J113

In the table below we listed the electrical specifications of 2SK170 and J113 JFET devices, this comparison is really helpful for a better understanding of this device.

  Gate to drain voltage (VGD)-40V35V
Gate to source cutoff voltage (VGS(OFF))-0.2 to -1.5V-0.5 to -3.0V
 Gate to source  voltage (V­GS)-40V-35V
Gate forward current (IG)10mA      50mA
Power dissipation (PD)400mW625mW
Junction temperature (TJ)-55 to 125°C-55 to 150°C
Input capacitance (Ciss)30pF28Pf
Noise figure (NF)1 to 10dB-

Graphical characteristics curves of 2SK170 JFET 

static characteristics of the 2SK170 JFET
static characteristics of the 2SK170 JFET

The figures show the static characteristics of the 2SK170 JFET, the graph plots with drain current vs drain to source voltage.

At the different gate-to-source voltage values, the drain value increases from the lowest value and then it increases towards a higher limit with respect to the drain-to-source voltage value.

noise figure vs drain current characteristics of 2SK170 JFET
noise figure vs drain current characteristics of 2SK170 JFET

The figure shows the noise figure vs drain current characteristics of 2SK170 JFET and the graph plots with noise figure vs drain current.

At constant drain to source voltage and frequency values, the noise figure value starts to decrease from the starting of the device.

2SK170 JFET-based PREAMP circuit

preamp circuit based on a 2SK170 JFET device
preamp circuit based on a 2SK170 JFET device

The figure shows the preamp circuit based on a 2SK170 JFET device, the circuit consists of three 2SK170 JFETs, some passive components, and an IN4148 diode.

When the input signal reaches the input capacitor, it will filter out the DC components and the signal reaches the JFET combination.

Applications of 2SK170 transistor  

  • Preamp circuit applications
  • Sensor circuit
  • Detector circuit
  • Audio mixer circuit
  • Vibration detector circuit
  • Low noise amplifier circuit
  • CT scanner circuit

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