Datenblatt-Suchmaschine für elektronische Bauteile |
|
OP279GSZ Datenblatt(PDF) 11 Page - Analog Devices |
|
OP279GSZ Datenblatt(HTML) 11 Page - Analog Devices |
11 / 16 page OP179/OP279 –11– REV. G UNITY-GAIN, SALLEN-KEY (VCVS) FILTERS High Pass Configurations Figure 14a is the HP form of a unity-gain 2-pole SK filter using an OP179/OP279 section. For this filter and its LP coun- terpart, the gain in the passband is inherently unity, and the signal phase is noninverting due to the follower hookup. For simplicity and practicality, capacitors C1-C2 are set equal, and resistors R2-R1 are adjusted to a ratio “N,” which provides the filter damping “ α” as per the design expressions. An HP design starts with the selection of standard capacitor values for C1 and C2, and a calculation of N. R1 and R2 are then calculated as per the figure expressions. In these examples, α (or 1/Q) is set equal to √2, providing a Butterworth (maximally flat) response characteristic. The filter corner frequency is normalized to 1 kHz, with resistor values shown in both rounded and (exact) form. Various other two-pole response shapes are also possible with appropriate selection of α. For a given response type (α), frequency can be easily scaled, using proportional R or C values. +VS –VS U1A OP279 1 3 2 4 8 IN R2 22k (22.508k ) R1 11k (11.254k ) C2 0.01 F R = R2 0.1 F Zf (HIGH PASS) C1 0.01 F GIVEN: ALPHA, F SET C1 = C2 = C ALPHA = 2/(N^0.5) = 1/Q N = 4/(ALPHA)^2 = R2/R1 R1 = 1/(2*PI*F*C* (N^0.5)) R2 = N*R1 1kHz BW SHOWN OUT 7 5 6 R = R1+R2 Zf (LOW PASS) GIVEN: ALPHA, F SET R1 = R2 = R ALPHA = 2/(M^0.5) = 1/Q N = 4/(ALPHA)^2 = C2/C1 PICK C1 C1 = M*C1 R = 1/(2*P1*F*C1* (M^0.5)) 1kHz BW SHOWN IN R2 11k (11.254k ) C2 0.01 F 0.1 F C1 0.02 F OUT U1B OP279 R1 11k (11.254k ) a. High Pass b. Low Pass Figure 14. Two-Pole Unity-Gain Sallen Key HP/LP Filters Low Pass Configurations In the LP SK arrangement of Figure 14b, R and C elements are interchanged, and the resistors are made equal. Here the C2/C1 ratio “M” is used to set the filter α, as noted. This design is begun with the choice of a standard capacitor value for C1 and a calcu- lation of M, which forces a value of “M × C1” for C2. Then, the value “R” for R1 and R2 is calculated as per the expression. For highest performance, the passive components used for tun- ing active filters deserve attention. Resistors should be 1%, low TC, metal film types of the RN55 or RN60 style, or similar. A Single-Supply Headphone Amplifier Because of its high speed and large output drive, the OP179/P279 makes for an excellent headphone driver, as illustrated in Figure 13. Its low supply operation and rail-to-rail inputs and outputs give a maximum signal swing on a single 5 V supply. To ensure maximum signal swing available to drive the headphone, the amplifier inputs are biased to V+/2, which is in this case 2.5 V. The 100 k Ω resistor to the positive supply is equally split into two 50 k Ω with their common point bypassed by 10 µF to pre- vent power supply noise from contaminating the audio signal. 16 50k 220 F LEFT HEADPHONE 10 F 50k 50k 100k 10 F LEFT INPUT +V + 5V 1/2 OP279 16 50k 220 F RIGHT HEADPHONE 10 F 50k 50k 100k 10 F RIGHT INPUT +V +V + 5V 1/2 OP279 Figure 13. A Single-Supply, Stereo Headphone Driver The audio signal is then ac-coupled to each input through a 10 µF capacitor. A large value is needed to ensure that the 20 Hz audio information is not blocked. If the input already has the proper dc bias, the ac coupling and biasing resistors are not required. A 220 µF capacitor is used at the output to couple the amplifier to the headphone. This value is much larger than that used for the input because of the low impedance of the head- phones, which can range from 32 Ω to 600 Ω. An additional 16 Ω resistor is used in series with the output capacitor to pro- tect the op amp’s output stage by limiting capacitor discharge current. When driving a 48 Ω load, the circuit exhibits less than 0.02% THD+N at low output drive levels (not shown). The OP179/OP279’s high current output stage can drive this heavy load to 4 V p-p and maintain less than 1% THD+N. Active Filters Several active filter topologies are useful with the OP179/OP279. Among these are two popular architectures, the familiar Sallen- Key (SK) voltage controlled voltage source (VCVS) and the multiple feedback (MFB) topologies. These filter types can be arranged for high pass (HP), low pass (LP), and band-pass (BP) filters. The SK filter type uses the op amp as a fixed gain voltage follower at unity or a higher gain, while the MFB structure uses it as an inverting stage. Discussed here are simplified, 2-pole forms of these filters, highly useful as system building blocks. |
Ähnliche Teilenummer - OP279GSZ |
|
Ähnliche Beschreibung - OP279GSZ |
|
|
Link URL |
Privatsphäre und Datenschutz |
ALLDATASHEETDE.COM |
War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |