AC Coupling With Improved Phase/Bandwidth
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
This AC coupling is used between the amplifier stages of a disk file read channel. The coupling blocks out DC offset and filters out low frequency noise. The improved phase characteristic of this pole/zero configuration permits locating the low frequency cutoff four to five times closer to the lowest signal frequency. Transient recovery time and low frequency noise attenuation are thereby optimized (e.g., read channel recovery from a write turn-off transient). Implementations (A) and (B) are similar, where R2 represents driver resistance in (A) and shunt load resistance in (B). In (A), an inductor is added in series with the normal AC coupling resistor. This is a minimum space passive implementation, but inductors are expensive and prone to picking up noise. Implementation (C) requires only resistors and capacitors.