OPA1641 Datasheet, PDF (24/31 Pages) Texas Instruments – High-Performance, JFET-Input AUDIO OPERATIONAL AMPLIFIERS

OPA1641, OPA1642, OPA1644
SBOS484C – DECEMBER 2009 – REVISED DECEMBER 2015
www.ti.com
8.2 Typical Application
The noise and distortion performance of the OPA164x family of amplifiers is exceptional in applications with high
source impedances which makes it an excellent choice in preamplifier circuits for moving magnet phono
cartridges. The high source impedance of the cartridge, and high gain required by the RIAA playback curve at
low frequency, requires an amplifier with both low input current noise, and low input voltage noise.
+15 V
RC 1.5k
LC 600mH
V_C
R1
47k
C1
150pF
+ + ^OPA1642
-
-15 V
R5
C5
100
100uF
Output
R6
100k
Moving-Magnet Phono Cartridge
R2
R3
118k
10k
R4
127
C4
100uF
C2
27nF
C3
7.5nF
Figure 38. Preamplifier Circuit for Vinyl Record Playback With Moving-Magnet Phono Cartridges
(Single Channel Shown)
8.2.1 Design Requirements
• Gain: 40 dB (1 kHz)
• RIAA Accuracy: ±0.5 dB (100 Hz to 20 kHz)
• Power Supplies: ±15 V
8.2.2 Detailed Design Procedure
Vinyl records are recorded using an equalization curve specified by the Recording Institute Association of
America (RIAA). The purpose of this equalization curve is to decrease the amount of space occupied by a grove
on the record and therefore maximize the amount of information able to be stored. Proper playback of music
stored on the record requires a pre-amplifier circuit that applies the inverse transfer function of the recording
equalization curve. The combination of the recording equalization and the playback equalization results in a flat
frequency response over the audio range as shown in Figure 39.
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