THAT1512S08-U Datasheet, PDF (4/8 Pages) List of Unclassifed Manufacturers – Low-Noise, High Performance Audio Preamplifier IC

Document 600031 Rev 08
Page 4 of 8
THAT 1510/1512 Low-Noise
High Performance Audio Preamplifier IC
Applications
Gain Setting
A single external resistor (RG) between the RG1
and RG2 pins is all that is needed to set the gain of the
THAT 1510/1512, according to the formulae:
for the 1510:
for the 1512:
A_V
=
1
+
10k
RG
A_V
=
0.5
+
5k
RG
or
where
AV is the voltage gain of the part.
Either part may reach unity gain, but the value
of RG required varies significantly between the two
parts. For the 1510, gain is 0dB when RG is infinite
(open); this is the minimum gain for the 1510. At
infinite RG, the 1512 reaches -6dB gain; this is the
minimum gain for the 1512. With RG=10kΩ, the
1512 reaches 0dB gain.
Overall gain accuracy depends on the tolerance
of RG and the accuracy of the internal thin-film resis-
tors connected to pins RG1 and RG2 in the 1510/1512
(RA & RB in Figure 1). These internal resistors have a
typical initial accuracy (at room temperature) of
±0.5%, and are typically stable with temperature to
within ±100 ppm/°C. Gain will drift with tempera-
ture based on the mismatch between the temperature
coefficient of the external RG and that of the internal
resistors RA & RB.
critical, a potentiometer may be used. In such appli-
cations, designers should take care in specifying the
element construction to avoid excess noise. The
potentiometer taper will set the circuit’s characteris-
tic of gain vs. pot rotation. Typically, reverse log
(reverse audio) taper elements offer the desired
behavior in which gain increases with clockwise
rotation (and lower values for RG). See THAT Design
Note 138 for a discussion of potentiometer taper and
gain for the 1510 and 1512 compared to similar
parts from other manufacturers.
Noise Performance
Both parts exhibit excellent voltage noise
performance of ~1 nV/√Hz at high gains. With
~2 pA/√Hz current noise, they are optimized for
relatively low source impedance applications, such as
dynamic microphones with typically a few hundred
ohm output impedances. But, because they have
different internal gain structures, the 1510 has
higher equivalent input noise at 0dB gain
(~57 nV/√Hz) than the 1512, which runs 4.5 dB
lower at ~34 nV/√Hz. The unusual and superior
topology of the THAT 1512 makes its noise perform-
ance comparable to some of the better discrete
designs currently available.
Inputs
For variable-gain applications where gain
accuracy is important, THAT recommends using
discrete, switched resistors for RG. Where continuous
control is required, or where gain accuracy is less
Simple Configurations
As shown in Figure 2, the 1510/1512 includes
protection diodes at all pins except V+ and V-.
V+
+In
-In
R_G1
R_G2
Input Stage
Output Stage
5k
5k
(10k)
-AV
-
-A_V
+
Out
5k
(10k)
5k
R_A
5k
Ref
R_B
5k
V-
Figure 2. THAT 1510 / 1512 Equivalent Circuit with Protection Diodes
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
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