The J112 is an industry-standard, high-speed N-Channel Junction Field-Effect Transistor (JFET) encapsulated in a compact TO-92 plastic through-hole package. Specifically engineered for low-resistance analog switching, chopper circuits, commutators, and audio muting applications, the J112 offers a low on-state resistance (R_DS(on) < 50>

Specifications

• Brand / Manufacturer: ON Semiconductor / Fairchild / InterFET / Industry Standard
• Part Number: J112
• Transistor Type: N-Channel Symmetrical Depletion-Mode JFET
• Drain-Source Voltage (V_DS): 35V
• Drain-Gate Voltage (V_DG): 35V
• Gate-Source Reverse Breakdown Voltage (V_GSR): -35V
• Gate Current (I_G): 50mA
• Zero-Gate-Voltage Drain Current (I_DSS): Minimum 5.0mA (Typically 5.0mA to 30mA @ V_DS = 15V, V_GS = 0V)
• Gate-Source Cutoff Voltage (V_GS(off)): -1.0V to -5.0V (at V_DS = 15V, I_D = 1.0µA)
• Static Drain-Source On-Resistance (R_DS(on)): < 50>GS = 0V, I_D = 1.0mA)
• Common-Source Input Capacitance (C_iss): Max 28pF (at V_DS = 0V, V_GS = -10V, f = 1.0MHz)
• Common-Source Reverse Transfer Capacitance (C_rss): Max 5.0pF (at V_DS = 0V, V_GS = -10V, f = 1.0MHz)
• Turn-On Time (t_on): Typically < 4>
• Turn-Off Time (t_off): Typically < 25ns>
• Total Device Dissipation (P_D): 350mW to 625mW (at T_A = 25°C)
• Operating Junction & Storage Temperature Range: -55°C to +150°C
• Package / Case: TO-92 (3-Pin Through-Hole: Pin 1: Drain, Pin 2: Source, Pin 3: Gate)

Features

• Low On-State Resistance (R_DS(on) ≤ 50Ω): Ensures minimal insertion loss and low signal distortion across analog signal paths.
• Moderate Pinch-Off Voltage (-1.0V to -5.0V): Easier to turn fully OFF using standard low-to-medium negative logic supply rails compared to the J111.
• Ultra-Fast Switching Transitions: Nanosecond switching speeds provide crisp, low-latency analog gating without large propagation delays.
• Symmetrical Depletion-Mode Channel: Drain and Source terminals are fully interchangeable for bidirectional AC/DC analog signal handling.
• High Breakdown Margin (35V): Easily handles standard ±12V and ±15V op-amp signal swings without unwanted junction clipping.

Common Applications

• Analog Signal Switches & Routing: Precision low-loss signal switching in audio mixing consoles, synthesizers, and test gear.
• Audio Muting & Anti-Click Circuits: Silent, click-free muting for power amplifiers, DAC outputs, and preamps during power transitions.
• Sample-and-Hold / Chopper Amplifiers: High-speed charging/holding switches in data acquisition front-ends.
• Constant Current Sources / Limiters: Simple two-terminal constant current regulation when the Gate is shorted to the Source.
• Voltage-Controlled Attenuators: Smooth variable resistance element (VCR) in automated gain control (AGC) circuits.

Usage Tips

• Pinout Identification: Looking at the flat marked front face with leads pointing down, the pinout is Pin 1: Drain (D), Pin 2: Source (S), and Pin 3: Gate (G).
• Switching Control: The J112 is normally ON at V_GS = 0V. To ensure complete turn-off across the entire waveform, pull the Gate negative relative to the Source by at least -5V to -7V (exceeding the peak negative voltage of the switched analog signal).
• Gate Over-Voltage Protection: Always place a series 10kΩ resistor or a fast switching diode in series with the gate to prevent forward-biasing the Gate-Channel PN junction (V_GS must not exceed +0.7V).
• Constant Current Diode Mode: Tie Gate (Pin 3) directly to Source (Pin 2) to create a two-terminal current regulator delivering a fixed I_DSS current.

Datasheet