ADA4505-2ARMZ-R2 Analog Devices Inc, ADA4505-2ARMZ-R2 Datasheet - Page 15

• Manufacturer Part Number: ADA4505-2ARMZ-R2
• Description: IC OPAMP GP R-R 50KHZ DUAL 8MSOP
• Manufacturer: Analog Devices Inc

Specifications of ADA4505-2ARMZ-R2

• Design Resources: Precision Pulse Oximeter LED Current Sinks Using ADA4505-2, ADR1581, and ADG1636 (CN0125)
• Amplifier Type: Voltage Feedback
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• Slew Rate: 0.006 V/µs
• Gain Bandwidth Product: 50kHz
• Current - Input Bias: 0.5pA
• Voltage - Input Offset: 500µV
• Current - Supply: 7µA
• Current - Output / Channel: 40mA
• Voltage - Supply, Single/dual (±): 1.8 V ~ 5 V, ±0.9 V ~ 2.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -

The charge pump has been carefully designed so that switching
noise components at any frequency, both within and beyond the
amplifier bandwidth, are much lower than the thermal noise floor.
Therefore, the spurious-free dynamic range (SFDR) is limited
only by the input signal and the thermal or flicker noise. There
is no intermodulation between input signal and switching noise.
Figure 50 displays a typical front-end section of an operational
amplifier with an on-chip charge pump.
V
+IN
V
PP
B
Figure 50. Typical Front-End Section of an Op Amp
V
PP
Q1
= POSITIVE PUMPED VOLTAGE = V
with Embedded Charge Pump
Q2
–IN
V
V
DD
SS
RAIL-TO-RAIL
CASCODE
OUTPUT
STAGE
STAGE
AND
DD
+ 1.8V
OUT
Rev. 0 | Page 15 of 20
Figure 51, input offset voltage vs. input common-mode voltage
response, shows the typical response of two devices from Figure 7.
Figure 51 has been expanded so that it is easier to compare with
Figure 49, typical input offset voltage vs. common-mode voltage
response in a dual differential pair input stage op amp.
This solution improves the CMRR performance tremendously.
For instance, if the input varies from rail-to-rail on a 2.5 V
supply rail, using a part with a CMRR of 70 dB minimum, an
input-referred error of 790 μV is introduced. Another part with
a CMRR of 52 dB minimum generates a 6.3 mV error. The
ADA4505-2 CMRR of 90 dB minimum causes only a 79 μV
error. As with the PSRR error, there are complex ways to minimize
this error, but the ADA4505-2 solves this problem without
incurring unnecessary circuitry complexity or increased cost.
Figure 51. Input Offset Voltage vs. Input Common-Mode Voltage Response
–100
–150
–200
–250
–300
(Powered by a 5 V Supply; Results of Two Units Are Displayed)
300
250
200
150
100
–50
50
0
0
V
T
SY
A
0.5
= 25°C
= 5V
1.0
1.5
2.0
V
CM
2.5
(V)
3.0
3.5
ADA4505-2
4.0
4.5
5.0