EC5742｜Super Low power, CMOS,Rail-to-Rail Operational Amplifier

General Description

The ​​ EC5742 ​​ series ​​ amplifiers ​​ are ​​ single ​​ supply, ​​ low ​​ power ​​ CMOS ​​ dual ​​ operational ​​ amplifier, ​​ these ​​ amplifiers offer ​​ bandwidth ​​ of ​​ 9KHz, ​​ rail-to-rail ​​ inputs ​​ and ​​ outputs, ​​ and ​​ single-supply ​​ operation ​​ from ​​ 1.4V ​​ to ​​ 5.5V. ​​ Low quiescent ​​ supply current ​​ of ​​ 1μA and very low input ​​ bias ​​ current ​​ of ​​ 1pA make the devices ​​ an ideal choice for ​​ low offset, ​​ low ​​ power ​​ consumption ​​ and ​​ high ​​ impedance applications ​​ such ​​ as ​​ smoke ​​ detectors, ​​ photodiode amplifiers, and other sensors.

The EC5742 ​​ is ​​ available ​​ in ​​ SOP-8 ​​ and ​​ MSOP-8 ​​ packages. The ​​ extended ​​ temperature range ​​ of ​​ -40∘C ​​ to ​​ +85∘Cover all supply voltages offers additional design flexibility.

Features

◆Single-Supply Operation from +1.4V to +5.5V

◆Rail-to-Rail Input/Output

◆Gain-Bandwidth Product: 9KHz

◆Low Input Bias Current: 1pA

◆Low Offset Voltage: 1mV

◆Quiescent Current: 500nA/Amplifier

◆Available in Space-Saving Packages:

◆SOP-8 and MSOP-8 Packages

Applications

◆Portable Equipment

◆Mobile Communications

◆Smoke Detector

◆Sensor Interface

◆Medical Instrumentation

◆Battery-Powered Instruments

◆Handheld Test Equipment

Pin Configurations

EC5742 SOP8 and MSOP8 (Top View)

Figure 1. Pin Assignment Diagram (SOP8 and MSOP8 Package)

Note: Please see section “Part Markings” for detailed Marking Information.

Ordering Information

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ EC5742NN ​​ - XX ​​ X

Application Information

◆Size

EC5742 series op amps are unity-gain stable and suitable for a wide range of general-purpose applications. The small footprints of the EC5742 series packages save space on printed circuit boards and enable the design of smaller electronic products.

◆Power Supply Bypassing and Board Layout

EC5742 series operates from a single 1.4V to 5.5V supply or dual ±0.7V to ±2.75V supplies. For best performance,

a 0.1Μf ceramic capacitor should be placed close to the VDD pin in single supply operation. For dual supply operation, both VDD and VSS supplies should be bypassed to ground with separate 0.1μF ceramic capacitors.

◆Low Supply Current

The low supply current (1.4μA) of EC5742 series will help to maximize battery life. They are ideal for battery powered systems.

◆Operating Voltage

EC5742 series operate under wide input supply voltage (1.4V to 5.5V).In addition, all temperature specifications

apply from -40∘C ​​ to ​​ +125∘C. ​​ Most behavior remains unchanged throughout the full operating voltage range.

These guarantees ensure operation throughout the single Li-Ion battery lifetime.

◆Rail-to-Rail Input

The ​​ input ​​ common-mode ​​ range ​​ of ​​ EC5742 ​​ series ​​ extends ​​ 100mV ​​ beyond ​​ the ​​ supply ​​ rails ​​ (VSS-0.1V ​​ to ​​ VDD+0.1V). This ​​ is achieved by using complementary input stage. For normal operation, inputs should be limited to this range.

◆Rail-to-Rail Output

Rail-to-Rail output swing provides maximum possible dynamic range at the output. This is particularly important when operating in ​​ low ​​ supply ​​ voltages. ​​ The ​​ output ​​ voltage ​​ of ​​ EC5742 ​​ series ​​ can ​​ typically ​​ swing ​​ to ​​ less ​​ than ​​ 10mV ​​ from ​​ supply ​​ rail ​​ in ​​ light resistive loads (>100kΩ), and 60mV of supply rail in moderate resistive loads (10kΩ).

◆Capacitive Load Tolerance

The EC5742 series can directly drive 250pF capacitive load in unity-gain without oscillation. Increasing the gain enhances the amplifier’s ​​ ability to ​​ drive ​​ greater ​​ capacitive loads. ​​ In ​​ unity-gain ​​ configurations, ​​ the ​​ capacitive load ​​ drive ​​ can ​​ be improved ​​ by inserting an isolation resistor RISO in series with the capacitive load, as shown in Figure 1.

The ​​ bigger ​​ the ​​ RISO ​​ resistor ​​ value, ​​ the ​​ more ​​ stable ​​ VOUT ​​ will ​​ be. ​​ However, ​​ if ​​ there ​​ is ​​ a ​​ resistive ​​ load ​​ RL in ​​ parallel ​​ with ​​ the capacitive load, a voltage divider (proportional to RISO/RL) is formed, this will result in a gain error. The circuit in Figure 2 is an improvement to the one in Figure 1. RF provides the DC accuracy by feed-forward the VIN to RL. CF and RISO serve to counteract the loss of phase margin by feeding the high frequency component of the output signal back to the amplifier’s inverting input, thereby preserving the phase margin in the overall feedback loop. Capacitive drive can be increased by increasing the value of CF. This in turn will slow down the pulse response.

◆Differential amplifier

The differential amplifier allows the subtraction of two input voltages or cancellation of a signal common the two inputs. It is useful as a computational amplifier in making a differential to single-end conversion or in rejecting a common mode signal. Figure 3 shown the differential amplifier using EC5741.

◆Instrumentation Amplifier

The input impedance of the previous differential amplifier is set by the resistors R1, R2, R3, and R4. To maintain the high input ​​ impedance, ​​ one ​​ can ​​ use a ​​ voltage follower ​​ in front ​​ of ​​ each input ​​ as ​​ shown in the following two instrumentation amplifiers.

◆Three-Op-Amp Instrumentation Amplifier

The quad EC5742 can be used to build a three-op-amp instrumentation amplifier as shown in Figure 4.

The amplifier in Figure 4 is a high input impedance differential amplifier with gain of R2/R1. The two differential voltage followers assure the high input impedance of the amplifier.

◆Two-Op-Amp Instrumentation Amplifier

EC5742 can also be used to make a high input impedance two-op-amp instrumentation amplifier as shown in Figure 5.

◆Single-Supply Inverting ​​ Amplifier

The inverting amplifier is shown in Figure 6. The capacitor C1 is used to block the DC signal going into the AC signal source VIN. The value of R1 and C1 set the cut-off frequency to fC=1/(2πR1C1). The DC gain is defined by VOUT=-(R2/R1)VIN

◆Low Pass Active Filter

The low pass active filter is shown in Figure 7. The DC gain is defined by –R2/R1. The filter has a -20dB/decade roll-off after its corner frequency fC=1/(2πR3C1).

◆Sallen-Key 2nd Order Active Low-Pass Filter

EC5742 can be used to form a 2ed order Sallen-Key active low-pass filter as shown in Figure 8. The transfer function from VIN to

◆Sallen-Key 2nd Order high-Pass Active Filter

The 2nd order Sallen-key high-pass filter can be built by simply interchanging those frequency selective components R1, R2, C1, and C2 as shown in Figure 9.

Electrical Characteristics

◆Absolute Maximum Ratings

Note: Stress greater than those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions outside those indicated in the operational sections of this specification are not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.

◆Electrical Characteristics

(VDD = +5V, Vss = 0V, VCM = VDD/2, VOUT = VDD/2, RL=100K tied to VDD/2, SHDNB = VDD, TA = -40∘C to 85∘C, unless otherwise noted. Typical values are at TA =+25C.) (Notes 1)

◆Typical performance characteristics

TA =+25∘C,VDD = +5V, Vss = 0V, VCM = VDD/2 , VOUT = VDD/2, RL=100K tied to VDD/2, CL=60pF,unless otherwise noted.

Package Information

MSOP8