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FEATURES 

DIRECT REPLACEMENT FOR SILICONIX U309 

OUTSTANDING HIGH FREQUENCY GAIN  

LOW HIGH FREQUENCY NOISE 

NF = 2.7dB 

ABSOLUTE MAXIMUM RATINGS @ 25°C

Maximum Temperatures 

Storage Temperature ‐55°C to +150°C 

Operating Junction Temperature ‐55°C to +135°C 

Maximum Power Dissipation 

Continuous Power Dissipation  

500mW 

MAXIMUM CURRENT

Gate Current 

10mA 

MAXIMUM VOLTAGES 

Gate to Drain Voltage or  Gate to Source Voltage  ‐25V 

  

  

LSU309 ELECTRICAL CHARACTERISTICS @ 25°C (unless otherwise noted)

SYMBOL 

CHARACTERISTIC 

MIN 

TYP. 

MAX 

UNIT 

CONDITIONS 

Gate to Source Breakdown Voltage ‐25 

‐‐ 

‐‐ 

V 

Gate to Source Forward Voltage 

0.7 

‐‐ 

1 

Gate to Source Cutoff Voltage ‐1 

‐‐ 

‐4 

Drain to Source Saturation Current

12 

‐‐ 

30 

mA 

Gate Operating Current (Note 3) 

‐‐ 

‐15 

‐‐ 

pA 

Drain to Source On Resistance 

‐‐ 

35 

‐‐ 

Ω 

VGS = 0V,  ID = 1mA 

  

 

 

 

 

 

LSU309 DYNAMIC ELECTRICAL CHARACTERISTICS @ 25°C (unless otherwise noted) 

SYMBOL 

CHARACTERISTIC 

MIN 

TYP. 

MAX 

UNIT 

CONDITIONS 

Forward Transconductance 

10 

14 

‐‐ 

mS 

VDS = 10V,   ID = 10mA , f = 1kHz 

Output Conductance 

‐‐ 

110 

250 

µS 

Input Capacitance 

‐‐ 

4 

5 

pF 

VDS = 10V,   VGS = ‐10V , f = 1MHz  

Reverse Transfer Capacitance 

‐‐ 

1.9 

2.5 

Equivalent Noise Voltage 

6 

‐‐ 

‐‐ 

nV/√Hz 

  

 

 

 

 

 

LSU309 HIGH FREQUENCY CHARACTERISTICS @ 25°C (unless otherwise noted) 

SYMBOL 

CHARACTERISTIC 

MIN 

TYP 

MAX 

UNIT 

CONDITIONS 

NF 

Noise Figure 

f = 105MHz 

‐‐ 

1.5 

‐‐ 

dB  

 

 

 

f = 450MHz 

‐‐ 

2.7 

‐‐ 

dB 

Power Gain

f = 105MHz 

‐‐ 

16 

‐‐ 

 

f = 450MHz 

‐‐ 

11.5 

‐‐ 

 

Forward Transconductance 

f = 105MHz 

‐‐ 

14 

‐‐ 

 

 

mS 

f = 450MHz 

‐‐ 

13 

‐‐ 

Output Conductance 

f = 105MHz 

‐‐ 

0.16 

‐‐ 

f = 450MHz 

‐‐ 

0.55 

‐‐ 

  

 

  

 

  

 

  

 

  

 

LSU309

N-CHANNEL JFET

Linear Systems replaces discontinued Siliconix U309

The LSU309 is a high frequency n-channel JFET

offering a wide range and low noise performance. The

hermetically sealed TO-18 package is well suited for

high reliability and harsh environment applications.

(See Packaging Information).

LSU309 Applications:

UHV / VHF Amplifiers

Mixers

Oscillators

LSU309 Benefits:

High Power Low Noise gain

Dynamic Range greater than 100dB

Easily matched to 75Ω input

Micross Components Europe

Available Packages:

LSU309 in TO-18

LSU309 in bare die.

Please contact Micross for full

package and die dimensions

Note 1 ‐ Absolute maximum ratings are limiting values above which LSU309 serviceability may be impaired.  

Note 2 ‐ Pulse test : PW ≤ 300µs, Duty Cycle ≤ 3% 

Note 3 ‐ Measured at optimum input noise match 

Tel: +44 1603 788967

TO-18 (Bottom View)