مخطط الأطراف

مخطط أطراف مضخم عمليات JFET مزدوج TL072

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الأطراف

• 1: OUT1 — output of amplifier 1; Class-AB output stage that isn't rail-to-rail, typically needs a couple of volts of headroom from both V+ and V− before it clips
• 2: IN1− — inverting input of amp 1; the JFET gate draws essentially no bias current, so it won't load down a high-impedance source like a piezo pickup or a photodiode the way a bipolar-input part would
• 3: IN1+ — non-inverting input of amp 1
• 4: V− — negative supply rail; on a typical split-supply audio circuit this sits at −9V to −15V, not ground — unlike the LM358, the input stage can't swing down to V−, so this part won't bias correctly if dropped into an LM358-style single 5V-rail circuit
• 5: IN2+ — non-inverting input of amp 2, a fully separate amplifier from amp 1 apart from sharing pins 4 and 8
• 6: IN2− — inverting input of amp 2
• 7: OUT2 — output of amp 2, same Class-AB behavior and headroom limits as OUT1
• 8: V+ — positive supply rail; datasheet-recommended range is ±3V to ±18V split supply (36V absolute max across V+ to V−), commonly run at ±9V or ±15V in audio gear

المواصفات

الملاحظات

• Recommended operating range is a ±3V to ±18V split supply, with 36V total (V+ to V−) as the absolute maximum — most audio and effects-pedal designs run it at ±9V or ±15V rather than the single 3–5V rail an LM358 happily tolerates.
• JFET inputs pull essentially no bias current — typically well under 1nA, commonly cited around tens of pA — versus the LM358's tens-of-nA bipolar input current, which is why the TL072 is the default choice for high-impedance sources (guitar pickups, piezo elements, photodiodes). The tradeoff is that the input common-mode range doesn't reach V−, so unlike the LM358 it isn't suited to ground-referenced single-supply circuits.
• Output is not rail-to-rail: expect roughly 2–3V of headroom lost at each end of the supply before the output clips, more under heavier load.
• TI's datasheet lists output short-circuit protection, but continuous output current is still only in the tens of mA — fine for feeding the next stage or a line-level load, not enough to drive a relay coil or a motor directly.
• With a ~3MHz gain-bandwidth and ~13V/µs slew rate it's noticeably faster than the LM358 (~1MHz, ~0.3V/µs); that extra bandwidth makes supply decoupling matter more in practice — a 0.1µF ceramic capacitor right at pins 4 and 8 is standard practice to keep it from oscillating.
• Same pinout as the TL082 and pin-compatible with several other dual op-amps in this footprint (NE5532, RC4558, etc.), which is why it's a common swap-in ('op-amp rolling') on guitar pedal and preamp boards.
• JFET gate inputs are static-sensitive — use normal ESD handling precautions, more so than with a bipolar-input part like the LM358.