Why BJT is used in bandgap?
Turns out BJT transistors makes very good diodes; and forward biased base emitter voltage versus collector current has excellent diode characteristics for bandgap.
What is internal bandgap?
A bandgap voltage reference is a temperature independent voltage reference circuit widely used in integrated circuits. It produces a fixed (constant) voltage regardless of power supply variations, temperature changes, or circuit loading from a device.
What is PTAT and Ctat?
PTAT, proportional to absolute temperature; CTAT, complementary to absolute temperature.
What is bandgap trimming?
Due to process variation, bandgap circuit is not operating with the designed current and/or current ratio in the 2 diodes. It will produce a different voltage and curvature over temperature. Trimming adjusts the resistors and hence the current back to design intent.
Is it better to use diodes or BJTS at the bandgap core?
Turns out BJT transistors makes very good diodes; and forward biased base emitter voltage versus collector current has excellent diode characteristics for bandgap. In bipolar process, simple diode is actually not easy to make.
What is current mirror circuit?
A current mirror is a circuit designed to copy a current through one active device by controlling the current in another active device of a circuit, keeping the output current constant regardless of loading. The current being “copied” can be, and sometimes is, a varying signal current.
How does a PTAT work?
A proportional to absolute temperature (PTAT) sensor is capable of reducing a sensing error resulted from a mismatch between circuit components. The PTAT sensor includes a control unit, a sensing unit and a calculation unit. The control unit generates a control signal.
What is a typical acceptable temperature coefficient of a bandgap reference?
Typical bandgap references can achieve temperature coefficients as low as 20 ppm/°C.
What is a PTAT sensor?
What is electronic trimming?
Trimming the output voltage of a power supply simply means adjusting the voltage by a small amount. By convention, the term trimming is used for applications where the power supply has a specified nominal output voltage and the user is able to change the output voltage by about ten percent or less.
What is trimming in IC design?
Laser trimming is the controlled alteration of the attributes of a capacitor or a resistor by a laser beam. Selecting one or more components on the circuit and adjusting them with the laser achieves this. The trim changes the resistor or capacitor value until the nominal value has been reached.
Why MOS is better than BJT?
mosfet is much faster than bjt because in a mosfet, only majority carriers are the current. the device switches much faster than bjt and is therefore used for switching smps power. mosfet does not suffer huge variations of point q, it’s the opposite we see in bjt.
What is a bandgap reference?
By definition a bandgap reference is a voltage reference of which the output voltage is referred to the bandgap energy of the used semiconductor. The first bandgap reference was proposed by Robert Widlar in 1971. It used conventional junction isolated bipolar technology to make a stable low voltage (1.220 V) reference.
What is a Brokaw bandgap reference?
Brokaw bandgap reference is a voltage reference circuit widely used in integrated circuits, with an output voltage around 1.25 V with low temperature dependence. This particular circuit is one type of a bandgap voltage reference, named after Paul Brokaw, the author of its first publication.
What is a temperature-independent bandgap?
Like all temperature-independent bandgap references, the circuit maintains an internal voltage source that has a positive temperature coefficient and another internal voltage source that has a negative temperature coefficient. By summing the two together, the temperature dependence can be canceled.
How to calculate the bandgap narrowing of impurity concentration?
Results giving the bandgap narrowing (A Vs.) as a function of the impurity concentration (N) in the base (in the range of 4.10″-2.5 10″ cm-‘) are discussed. The experimental values of 0 V,o as a function of N can be fitted by: AVeo=V,IIno+V (InZN +CD where V,, No and C are constants.