Philips Semiconductors

Product specification

NE/SA5230

Low voltage operational amplifier

1994 Aug 31

8

THERMAL CONSIDERATIONS

When using the NE5230, the internal power dissipation capabilities

of each package should be considered. Philips Semiconductors

does not recommend operation at die temperatures above 110

°C in

the SO package because of its inherently smaller package mass.

Die temperatures of 150

°C can be tolerated in all the other

packages. With this in mind, the following equation can be used to

estimate the die temperature:

(1)

Where

T

T

P

+ (I

q

board mounting

See the packaging section for information regarding other methods

of mounting.

The maximum supply voltage for the part is 15V and the typical

supply current is 1.1mA (1.6mA max). For operation at supply

temperature and varies no more than 100

µA between 25°C and

either temperature extreme.

Operation at higher junction temperatures than that recommended is

possible but will result in lower MTBF (Mean Time Between

Failures). This should be considered before operating beyond

recommended die temperature because of the overall reliability

degradation.

DESIGN TECHNIQUES AND APPLICATIONS

The NE5230 is a very user-friendly amplifier for an engineer to

design into any type of system. The supply current adjust pin (Pin 5)

can be left open or tied through a pot or fixed resistor to the most

negative supply (i.e., ground for single supply or to the negative

supply for split supplies). The minimum supply current is achieved

by leaving this pin open. In this state it will also decrease the

bandwidth and slew rate. When tied directly to the most negative

programming of the current-control pin depends on the trade-offs

which can be made in the designer’s application. The graph in

the supply current can be varied anywhere over the range of 100

µA

to 600

µA for a supply voltage of 1.8V. An external resistor can be

inserted between the current control pin and the most negative

supply. The resistor can be selected between 1

Ω to 100kΩ to

provide any required supply current over the indicated range. In

addition, a small varying voltage on the bias current control pin could

be used for such exotic things as changing the gain-bandwidth for

voltage controlled low pass filters or amplitude modulation.

Furthermore, control over the slew rate and the rise time of the

amplifier can be obtained in the same manner. This control over the

slew rate also changes the settling time and overshoot in pulse

response applications. The settling time to 0.1% changes from 5

µs

at low bias to 2

µs at high bias. The supply current control can also

be utilized for wave-shaping applications such as for pulse or

triangular waveforms. The gain-bandwidth can be varied from

between 250kHz at low bias to 600kHz at high bias current. The

slew rate range is 0.08V/

µs at low bias and 0.25V/µs at high bias.

a. Unity Gain Bandwidth vs Power Supply Current for

Several Supply Voltages

800

700

600

500

400

300

200

100

100

200

300

400 500 600 700

UNITY GAIN BANDWIDTH (kHz)

TA = 25°C

VCC = 15V

VCC = 12V

VCC = 9V

VCC = 6V

VCC = 3V

VCC = 2V

VCC = 1.8V

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

100

101

102

103

104

105

RADJ (Ω)

SL00253

Figure 4.

40kHz for the maximum bias current setting and greater than 10kHz

at the minimum bias current setting.

If extremely low signal distortion (<0.05%) is required at low supply

common-mode signal range. This can be accomplished by proper

bias selection or by using an inverting amplifier configuration.

Most single supply designs necessitate that the inputs to the op amp

signal swing is within the working common-mode range of the

amplifier. This leads to another helpful and unique property of the

NE5230 that other CMOS and bipolar low voltage parts cannot

achieve. It is the simple fact that the input common-mode voltage

can go beyond either the positive or negative supply voltages. This

benefit is made very clear in a non-inverting voltage-follower

configuration. This is shown in Figure 5 where the input sine wave

allows an undistorted output sine wave which will swing less than

100mV of either supply voltage. Many competitive parts will show

severe clipping caused by input common-mode limitations. The

NE5230 in this configuration offers more freedom for quiescent

biasing of the inputs close to the positive supply rail where similar op

amps would not allow signal processing.