When V REF approaches the threshold, the I CA rises to 300–500 μA, but the output transistor remains closed. Residual cathode-anode current I CA, feeding the front-end circuit, stays within 100 and 200 μA. When V REF is safely below the 2.5 V threshold (point A on current-voltage curve), the output transistor is closed. The circuit does not provide protection against excessive current or overheating. The output open collector transistor, T11, can sink currents up to 100 mA, and is protected from polarity reversal with a reverse diode. The differential amplifier is made of two current sources (T8, T9) the positive difference of their currents sinks into the base of T10. This enables correct operation even when the cathode-anode voltage drops below 2.5 V, down to around 2.0 V minimum. There is no physical 2.5 V source: the actual internal reference is provided by a 1.2 V Widlar bandgap (transistors T3, T4, T5), driven by the input emitter followers T1, T6. This, however, is merely an abstraction: both functions are inextricably linked inside the TL431's front end. On a functional level the TL431 contains a 2.5 V voltage reference, and an open-loop operational amplifier that compares the input control voltage with the reference. The positive control voltage, V REF, is applied between reference input and the anode the output current, I CA, flows from the cathode to the anode. 'Base', 'collector' and 'emitter' of this 'transistor' are traditionally called reference (R or REF), cathode (C) and anode (A). The TL431 is a three-terminal bipolar transistor switch, functionally equivalent to an ideal n-type transistor with a stable 2.5 V switching threshold and no apparent hysteresis. Operation in the yellow zone is possible but not recommended. The green zone is the recommended high transconductance area, extending upward to maximum current rating. These functionally similar circuits may differ considerably in die size and layout, precision and speed characteristics, minimal operating currents and safe operating areas.Ĭurrent-voltage curve for small error voltages. In the 21st century, the original TL431 remains in production along with a multitude of clones and derivatives (TL432, ATL431, KA431, LM431, TS431, 142ЕН19 and others). Texas Instruments introduced the TL431 in 1977. The TL431 is the de facto industry standard error amplifier circuit for switched-mode power supplies with optoelectronic coupling of the input and output networks. The circuit can control power transistors directly combinations of the TL431 with power MOS transistors are used in high efficiency, very low dropout linear regulators. The typical initial deviation of reference voltage from the nominal 2.495 V level is measured in millivolts, the maximum worst-case deviation is measured in tens of millivolts. With the use of an external voltage divider, a TL431 can regulate voltages ranging from 2.5 to 36 V, at currents up 100 mA. (jrr-at-flippers-dot-com for those who do not have their browser set to open their email client)Īll information on this site is Copyright (©) 1997 through 2022 by John's Jukes Ltd.The TL431 is a three-terminal adjustable precision shunt voltage regulator integrated circuit. Seeburg # Industry # NTE/ECG/TCG # (click here for other subs for the ECG #s) Transistor Part number cross reference (from Ryan's Vending in Canada): It is 16mb in size, but very handy to have! Now I have scanned the HAB Seeburg cross reference and it contains info on the original specificationsįor the Seeburg semiconductors. Note: We DO NOT STOCK THESE TRANSISTORS - THIS IS A PUBLIC SERVICE ONLY NOTE: The #12 and the #19 lamps, although the same shape and size, are NOT interchangeable (without modifying the circuit)! The #15 lamp though should NOT be used in places where the #12 lamp is used, even though the slightly lower voltage is OK, the #15 lamp’s glass bulb is that much bigger (3 mm) than the #12 lamp’s glass bulb, and a #15 lamp often has to be forced into the #12 lamp’s spot! NASTY JOB TO DO IN THE FIRST PLACE, AND CAN BE NASTY TO FIX AFTER THE EVENT! NOTE: Although the 7 volt #15 lamp is visibly fairly similar to the 6.3 volts #12 lamp, the glass bulb is distinctly larger on the #15 lamp and that allows for a much larger coiled filament to be used in the #15 lamp, and therefore, all things being equal, the #15 lamp will burn much brighter than a #12 lamp if both operate on the same voltage. Seeburg bulb cross-reference:(bulb info thanks to Erwin Boot!)

Transistor cross references