Current generating circuit

A technology for generating circuits and currents, applied in the direction of adjusting electrical variables, control/regulating systems, instruments, etc., can solve the problems of limiting maximum gain, deterioration of good linear adjustment rate, etc., to improve linear adjustment rate, reduce impact ionization effect, The effect of reducing the impact

Active Publication Date: 2010-09-08
FREMONT MICRO DEVICES SHENZHEN LTD
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  • Abstract
  • Description
  • Claims
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Problems solved by technology

However, at higher supply Vcc voltages, the impact ionization effect limits the maximum gain achievable with the cascode structure because it introduces a small signal from drain to substrate instead of drain to source resistance
The effect of impact ionization degrades the good linear regulation rate at low voltage operation

Method used

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Embodiment Construction

[0018] Figure 2 shows the conventional cascode structure used to improve the poor linear adjustment rate caused by the insufficient output resistance of the current mirror. This structure can show satisfactory performance when most of the Vcc is not too high. However, with the increase of Vcc, the impact ionization effect on the N-type MOS transistor 100 which bears most of the voltage stress gradually becomes serious. The high gain of the cascode structure is limited, thereby deteriorating the linear regulation of the PTAT current. We know from the NodeB waveform in Figure 4 (the voltage waveform at NodeB point in Figure 4 is equal to the voltage waveform at NodeC point in Figure 2), when Vcc=6V, the voltage between the two ends of the 100 drain source in Figure 2 is added The voltage difference Vcc-|Vthp| (Vthp is the threshold voltage of pMOSFET), is greater than 5V.

[0019] Figure 3 shows the improved PTAT current generation circuit proposed by the present invention, wh...

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Abstract

The invention relates to a current generated circuit which can integrate an over-voltage reducing device; the current is in direct proportion with the temperature (PTAT); the current generated circuit comprises a first cascode current mirror circuit and a second cascode current mirror circuit which are connected between a power supply Vcc and the ground in series; and the current generated circuit also comprises an over- voltage reducing device for restraining the impact ionization effect. The application of the current generated circuit can effectively reduce the drain-source voltage on the cascode device so as to reduce the influence of the impact ionization effect, without affecting the minimum operating voltage; therefore, the current generated circuit keeps the maximum gain of the current mirror structure and fundamentally solves the influence of impact ionization on the cascode, thereby improving the current benchmark linear adjusting rate.

Description

technical field [0001] The present invention relates to current reference design technology, more specifically, relates to a proportional to temperature (PTAT) current generation circuit that improves the linear adjustment rate of the current reference. Background technique [0002] Voltage references are widely used in analog circuits, such as in LDO, ADC / DAC and so on. It can accurately output a voltage that is almost independent of the input voltage and temperature, and the relationship between the voltage reference and the input voltage is measured by the linear adjustment rate. A voltage reference with high linearity regulation is essential for devices with a wide input voltage range. Commonly used voltage references are based on voltage mode and current mode. The voltage mode uses two voltages with opposite stability coefficients, and adds a certain weighting factor to obtain a voltage that is almost independent of temperature. The current mode uses two currents wit...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G05F3/16
Inventor 谭润钦谷文浩许如柏
Owner FREMONT MICRO DEVICES SHENZHEN LTD
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