Key Specs

SpecValueConditionSource
ConfigurationN-ChannelDigi-Key
Current Rating Amps10mADigi-Key
Frequency400MHzDigi-Key
Gain-Digi-Key
Mounting TypeSurface MountDigi-Key
Noise Figure4dBDigi-Key
Output Power (Max)-Digi-Key
Package CaseTO-236-3, SC-59, SOT-23-3Digi-Key
Supplier Device PackageSOT-23-3Digi-Key
TechnologyJFETDigi-Key
Voltage Rated25 VDigi-Key
Voltage Test15 VDigi-Key

When To Use

  1. 400MHz RF front-end amplifier @ 10mA bias: The 400MHz frequency rating and 4dB noise figure make this JFET ideal for low-noise amplification in RF stages where low current and moderate gain are required. Using a device not rated for 400MHz risks gain roll-off and instability, causing degraded signal integrity or oscillations.

  2. Low-current analog switch in 25V signal path: The 25V voltage rating and surface-mount SOT-23-3 package suit switching small analog signals up to 25V with minimal distortion. A MOSFET with lower voltage rating would risk breakdown and latch-up under transient spikes.

  3. Low-noise buffer stage in precision sensor interface at 10mA: The 4dB noise figure and JFET input help preserve signal fidelity at low bias currents. A bipolar transistor designed for higher current would increase noise and offset, reducing measurement accuracy.

When Not To Use

  1. Load requiring >10mA continuous current: The 10mA current rating is too low for this application. Use a multi-phase buck controller capable of handling higher current loads safely and efficiently.

  2. Switching frequency above 500kHz for miniaturized power supply: The 400MHz rating applies to RF gain, not switch-mode power operation at >500kHz. For high-frequency switching power, choose a high-frequency buck controller designed for stable operation above 500kHz.

  3. Battery-powered device needing ultra-low quiescent current: The device’s bias current is fixed near 10mA, which is excessive for ultra-low power. Use a low-IQ PFM buck regulator optimized for μA-level quiescent current.

Application Notes

Pin numbers are package-specific. Verify against the datasheet pinout diagram before routing.

Gotchas

  1. [Voltage derating ignored at elevated temperature]: The 25V rating is absolute max at room temperature, but derating curves in the datasheet show reduced voltage tolerance above 85°C. Exceeding this derated voltage causes gradual gate oxide degradation, leading to increased leakage and eventual device failure. Fix: Verify operating voltage against thermal derating graphs and test under worst-case temperature conditions.

  2. [High source impedance load causing gain instability]: Using a high-impedance load connected directly at the source pin (pin 2) can cause oscillations at 400MHz due to the JFET’s Miller effect. Symptom: erratic output waveform with high-frequency ringing visible on the scope. Fix: Add a small series resistor (10–100Ω) at the source output to damp parasitic oscillations.

  3. [Startup with no minimum load]: The part requires a minimum bias current near 10mA for stable operation. Without a defined load current, the transistor may fail to reach its operating point, causing the output to saturate or remain low. Symptom: output appears dead or stuck at rail during startup. Fix: Include a bleed resistor or defined load to ensure minimum current flow at startup.

  4. [Incorrect PCB layout causing crosstalk between SW and input pins]: Routing the switching node (pin 3) traces too close or parallel to input pins 1 and 2 can induce unwanted coupling and cause intermittent noise spikes or jitter. Fix: Maintain physical separation with grounded guard traces and avoid overlapping routing layers for SW and input signals.