Requxrements are discussed for an Iunpllfier slutable for subsonic and supersonx tdx&?nce work nxth hot xlres. Such an empllfier needs to have a constant gain at low frequencies, ad a gain rlslng In proportion to frequency at h& frequenmes, UI order to compensate for the the-1 lag of tho hot vzrc. A fairly sharp cutoff 1s required at the high frequency end, and it is desirable that this cutoff ...