LT1806CS8 Linear Technology, LT1806CS8 Datasheet - Page 24

• Manufacturer Part Number: LT1806CS8
• Description: IC OPAMP R-R IN/OUT SNGL 8-SOIC
• Manufacturer: Linear Technology

Specifications of LT1806CS8

• Amplifier Type: General Purpose
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 140 V/µs
• Gain Bandwidth Product: 325MHz
• Current - Input Bias: 5µA
• Voltage - Input Offset: 100µV
• Current - Supply: 11mA
• Current - Output / Channel: 85mA
• Voltage - Supply, Single/dual (±): 2.5 V ~ 12.6 V, ±1.25 V ~ 6.3 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• -3db Bandwidth: -

LT1806/LT1807
1MHz Series Resonant Crystal Oscillator with Square
and Sinusoid Outputs
Figure 8 shows a classic 1MHz series resonant crystal
oscillator. At series resonance, the crystal is a low imped-
ance and the positive feedback connection is what brings
about oscillation at the series resonance frequency. The
RC feedback around the other path ensures that the circuit
does not fi nd a stable DC operating point and refuse to
oscillate. The comparator output is a 1MHz square wave
with a measured jitter of 28ps
40ps
however, is an excellent looking sine wave except for the
fact of the small high frequency glitch caused by the fast
TYPICAL APPLICATIONS
24
RMS
with a 3V supply. On the other side of the crystal,
V
S
R1
1k
R2
1k
2
3
Figure 8. LT1713 Comparator is Confi gured as a Series Resonant Crystal Oscillator.
The LT1806 Op Amp is Confi gured in a Q = 5 Bandpass Filter with f
C1
0.1μF
+
–
AT-CUT
6
Figure 9. Oscillator Waveforms with V
Middle Trace is Crystal Feedback to Pin 2 at LT1713. Bottom Trace is Buffered,
Inverted and Bandpass Filtered with a Q of 5 by the LT1806
1MHZ
LT1713
V
LE
S
5
1
7
RMS
4
210Ω
R4
1k
R3
1k
8
with a 5V supply and
SQUARE WAVE
3V/DIV
1V/DIV
1V/DIV
100pF
6.49k
R5
V
V
S
S
R6
162Ω
= 2.7V TO 6V
200ns/DIV
R9
S
2k
= 3V. Top Trace is Comparator Output.
edge and the crystal capacitance (middle trace of Figure 9).
Sinusoid amplitude stability is maintained by the fact that
the sine wave is basically a fi ltered version of the square
wave; the usual amplitude control loops associated with
sinusoidal oscillators are not immediately necessary.
One can make use of this sine wave by buffering and
fi ltering it, and this is the combined task of the LT1806. It
is confi gured as a bandpass fi lter with a Q of 5 and does
a good job of cleaning up and buffering the sine wave.
Distortion was measured at –70dBc and –60dBc on the
second and third harmonics.
1
therefore controllable. The important difference here is that any added amplitude stabilization loop
will not be faced with the classical task of avoiding regions of nonoscillation versus clipping.
Amplitude will be a linear function of comparator output swing, which is supply dependent and
C2
0.1μF
C3
100pF
R8
2k
18067 F09
2
3
–
+
100pF
C4
LT1806
4
V
C
S
7
= 1MHz
1 (NC)
15.8k
R7
6
SINE WAVE
18067 F08
18067fc
1