JST134Q-600D — 4A/600V Four-Quadrant TRIAC (TO-126)

What Are the Technical Specifications of JST134Q-600D?

Key numbers that matter: the gate spec is where this part lives or dies. I_GT 5/5/5/10mA means a single opto-triac class driver can fire it from a 3.3V or 5V MCU — but only if you feed the LED side enough current.

At 4A RMS, V_TM 1.55V works out to roughly 5–6W of on-state loss, and R_th(j-c) of 7.5°C/W decides how much copper that needs.

Per the JieJie JST134 datasheet (Rev A.1.0), the 4A rating holds at T_c ≤ 84°C. In a sealed appliance enclosure you're realistically at 2–3A — derate for your real case temperature, not the datasheet's.

When Should You Use (and NOT Use) the JST134Q-600D?

✅ Use JST134Q-600D when:

• AC phase control — dimmers and motor speed. The core TRIAC job: cut a portion of the sine wave to dim lamps or slow fans in the 1–3A range.
• ON/OFF AC switching where relay bounce and wear hurt. No contacts, no bounce, no arcing — silent switching for appliance controls.
• Zero-cross switching with an opto-triac driver. Switching near the zero crossing kills EMI — a classic appliance-control pattern.
• Loads that need the 10mA quadrant-4 trigger. Some DC-driven opto drivers only fire in certain quadrants; the D-class gate gives you all four.
• Small induction-motor starting circuits. Listed in the datasheet's own applications — with a snubber for the phase shift.

❌ Don't use JST134Q-600D when:

• You're switching DC. A triac only turns off when current through it drops below I_H — on DC it latches permanently. Use a MOSFET or relay.
• The load current is under ~20mA. Below holding current the device drops out every half-cycle. LED indicator strings and dry contacts are the wrong load.
• Heavily inductive loads without a snubber. Commutation dV/dt of 2.5V/µs will false-fire on motor back-EMF — plan the RC snubber.
• Continuous load above ~3A in a sealed box. 4A is a case-temperature rating; thermal derating is real.
• Mains above 600V or surge-heavy environments. The 3kV V_pp rating is a pulse spec, not a licence to skip varistors.

What Are the Alternatives to JST134Q-600D?

The socket decision in one line: JST134Q-600D when you want the JieJie footprint and cost profile; BT136-600D when your BOM already sources NXP-class TO-220; MAC4DSM when the line is surface-mount.

For a TO-126 to TO-220 swap, check the pinout first — both are T1/T2/G on pins 1/2/3, so the mechanical change is usually the only one. Same part in a bigger body means better R_th(j-c) for the same die.

What Are the Typical Applications of JST134Q-600D?

Resistive-load dimmers: Phase control on incandescent and resistive loads is the classic socket. The 4A rating covers a 480W dimmer at 120V or 920W at 230V with headroom for inrush on cold filaments.

Fan and small motor speed controllers: Series with the motor, with an RC snubber across the triac. The 120V/µs static dV/dt and 2.5V/µs commutation dV/dt give margin against motor back-EMF when the gate drive is clean.

Heating regulation: ON/OFF or phase-cut control for appliance heaters, soldering irons, and thermal regulators — the datasheet's listed "heating regulation" application. Zero-cross switching keeps the mains clean.

Induction motor starting circuits: The datasheet lists these explicitly. A triac in series with the start winding gives controlled ramp-up where a centrifugal switch wears out.

Appliance ON/OFF switching: Silent, bounce-free switching for the appliance class — the relay alternative clicks, arcs, and wears. With zero-cross firing you get the EMI profile of a relay and none of its contact life limits.

Why Buy JST134Q-600D from ICMASS?

Lot-tested gate parameters. We verify I_GT and I_H on lot samples before shipping. On a triac, a remarked or downgraded die shows up first in the trigger circuit — marginal gate current and early drop-out are the classic tells.

Cross-reference support for the whole TO-126/TO-220 socket. Not sure whether the socket wants the JST134Q, a BT136-class part, or a DPAK die? Send us the load type, RMS current, and whether the board is through-hole — we'll match the body and gate class.

BOM consolidation for appliance controls. The same control BOM carries the TRIAC, the opto-triac driver, and the snubber passives — one shipment covers the whole switching stage.

Same-day dispatch, 5–10 days worldwide. Orders before 15:00 CST ship same day via DHL or FedEx.

Frequently Asked Questions About JST134Q-600D

Q1: What is the JST134Q-600D?

A: A 4A, 600V four-quadrant TRIAC from JieJie Microelectronics in TO-126. It switches AC loads in both half-cycles from a single gate — the standard device for dimmers, fan speed control, and appliance ON/OFF switching in the 1–3A range.

Q2: What does the "D" suffix mean on JST134Q-600D?

A: It's the gate sensitivity class: I_GT ≤ 5mA in quadrants 1–3 and ≤ 10mA in quadrant 4. The "Q" means TO-126 package and "600" means 600V V_DRM/V_RRM. A "B" or "E" suffix variant has a different trigger class.

Q3: Can I trigger the JST134Q-600D directly from an MCU pin?

A: No — and this is the most common failure in beginner circuits. MCU pins deliver about 5mA and the gate needs 5–10mA with a clean return path. More importantly, the MCU's ground isn't the mains neutral. Use an opto-triac driver like the MOC3021 plus a gate resistor; it isolates the MCU and can supply the trigger current properly.

Q4: My triac circuit won't trigger — what should I check?

A: Check three things: gate current, gate reference, and quadrant. Is the drive delivering more than I_GT (5mA here, 10mA in quadrant 4)? Is the gate referenced to T1 (MT1) — not the load side? And is the polarity correct for the quadrant you're firing? All three show up repeatedly in real forum threads on dead triac circuits.

Q5: What's the difference between latching current and holding current?

A: Latching current (10mA, 20mA in quadrant 2) is what's needed at turn-on to establish conduction; holding current (7mA) is what keeps it conducting. The gate pulse must persist until load current exceeds latching current — a pulse that's too short or a load that's too light drops out every half-cycle.

Q6: My triac turns on by itself — why?

A: False triggering, usually from leakage current or dV/dt. The opto-triac driver's internal device leaks enough at high temperatures to fire the main triac. A 47–100Ω resistor from gate to T1 shunts that leakage, and an RC snubber across the triac handles fast voltage spikes.

Q7: Can I use the JST134Q-600D to switch DC?

A: No. A TRIAC turns off only when its current drops below holding current — on DC it latches and stays on until the supply dies. DC switching needs a MOSFET, relay, or IGBT.

Q8: How much current can the JST134Q-600D really switch?

A: 4A RMS at case temperature ≤ 84°C, derated from there. In a sealed enclosure or on a small board, plan for 2–3A continuous. The R_th(j-c) of 7.5°C/W means the tab's thermal path decides what you actually get.

Q9: Where can I buy the JST134Q-600D?

A: Contact ICMASS for current pricing and availability. Volume pricing typically lands in the $0.10–$0.25/unit range depending on quantity. We stock the TO-126 part and can quote same-day for your quantity.