7 Detailed Description

7.1 Overview

The REF30 is a series, precision bandgap voltage reference. The basic topology is shown in the Section 7.2.

Transistors Q1 and Q2 are biased so that the current density of Q1 is greater than that of Q2. The difference of

the two base-emitter voltages, Vbe1 – Vbe2, has a positive temperature coefficient and is forced across resistor

R1. This voltage is gained up and added to the base-emitter voltage of Q2, which has a negative coefficient. The

resulting output voltage is virtually independent of temperature. The curvature of the bandgap voltage, as shown

in Figure 6-10, is due to the slightly nonlinear temperature coefficient of the base-emitter voltage of Q2.

7.2 Functional Block Diagram

R

1

Q

2

Q

1

+

Vbe

1

+

Vbe

2

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7.3 Feature Description

7.3.1 Supply Voltage

The REF30 family of references features an extremely low dropout voltage. With the exception of the REF3012,

which has a minimum supply requirement of 1.8V, the REF30 can be operated with a supply of only 1mV above

the output voltage in an unloaded condition. For loaded conditions, a typical dropout voltage versus load is

shown on the front page.

The REF30 features a low quiescent current that is extremely stable over changes in both temperature and

supply. The typical room temperature quiescent current is 42μA, and the maximum quiescent current over

temperature is just 59μA. Additionally, the quiescent current typically changes less than 2.5μA over the entire

supply range, as shown in Figure 7-1.

Supply voltages below the specified levels can cause the REF30 to momentarily draw currents greater than the

typical quiescent current. Use a power supply with a fast rising edge and low output impedance to easily prevent

this issue.

42.5

42.0

41.5

41.0

40.5

40.0

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

V

(V)

IN

Figure 7-1. Supply Current vs Supply Voltage

REF30, REF30E

SBVS032J – MARCH 2002 – REVISED JULY 2025

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