LT1567I View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LT1567I' PDF : 16 Pages View PDF
LT1567
APPE DIX: OUTPUT OISE OF A OP A P I VERTI G A PLIFIER
R2
RS R1
–
+– VS
+
VOUT
RP
CS
1567 AP01
NOISE AT VOUT IN VRMS = VON IN V/√Hz • √fNBW
fNBW = NOISE BANDWIDTH
( ) ( ) VON =
R2 +
R1 + RS
1
2
•
VN2
+
R2
R1 + RS
2 • (VR12 + VSN2) + VR22 + (IN • R2)2
IF VSN AND RS = 0
THEN
( ) ( ) VON =
R2 +
R1
1
2
•
VN2
+
R2
R1
2 • VR12 + VR22 + (IN • R2)2
VON is the voltage noise density in V/√Hz at the inverter’s
output.
VN is the op amp’s voltage noise density in V/√Hz.
IN is the op amp’s current noise density in A/√Hz.
VSN is the voltage noise density of the input voltage source
VS with source resistance RS. (If VSN is less than one-half
the noise of resistor R1, then the calculation error when
omitting VSN is less than 4.3%.)
VR1 and VR2 is the voltage noise density of the thermal
noise of resistors (R1 + RS) and R2 respectively. Resistor
RS is typically smaller than R1 and is omitted from noise
calculations. The voltage noise density of the thermal
noise of a resistor R is approximately 0.128x√RnV/√Hz at
25°C.
The RP resistor noise at the op amp’s plus input is equal
to √(kT/CS) and is omitted from noise calculations. (If
CS = 0.1µF, the RP noise is 0.2µVRMS at 25°C, k = 1.38x
10–23 and T = 273°C + 25°C.)
The noise bandwidth (fNBW) is greater than a circuit’s
–3dB bandwidth. (For a 1st, 2nd or 3rd order Butterworth
filter, fNBW is 1.57x, 1.22x and 1.15x respectively the –
3dB bandwidth.)
Example: Calculate VON, the voltage noise density of an
LT1567 op amp inverter for R1 = R2 = 604Ω. With
VN = 1.4nV/√Hz and IN = 1pA/√Hz.
( ) ( ) VON =
604
+
1
2
•
(1.4
•10–9)2
+
604
604
604
2 • (0.128 •10–9 • √604)2 + (0.128 • 10–9 • √604)2 + (10–12 • 604)2
VON = 5.29nV/√Hz
1567fa
14
Share Link: 
