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[82.70.254.222]) by smtp.gmail.com with ESMTPSA id o6sm44813356wra.27.2019.07.17.06.38.06 (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 17 Jul 2019 06:38:07 -0700 (PDT) Date: Wed, 17 Jul 2019 14:38:05 +0100 From: Chris Wilson X-Priority: 3 (Normal) Message-ID: <993240756.20190717143805@gmail.com> To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Spam-Score: -0.2 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Hello rsgb, Some Class D LF / MF amps use a diode to DC restore the waveform after the FET driver chip to the gates. Why do they do this, I am thinking the negative part of the waveform would turn OFF the gate h [...] Content analysis details: (-0.2 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [2a00:1450:4864:20:0:0:0:32e listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (dead.fets[at]gmail.com) -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain X-Scan-Signature: 87966b345956c8ef3389b993f6a18f4e Subject: LF: DC restoration Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=PRIORITY_NO_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Hello rsgb, Some Class D LF / MF amps use a diode to DC restore the waveform after the FET driver chip to the gates. Why do they do this, I am thinking the negative part of the waveform would turn OFF the gate harder, assuming the positive part is adequate to turn the gates ON hard enough? Is there any point in using the modern FET's designed to have a negative rail to turn the gates off hard? Cree do the Wolfspeed ones with this feature. I have also noticed that with amps where the input to the driver is capacitively coupled adding a DC restoration diode makes the waveform pretty much exactly 50 / 50 mark space, whereas without one this is not the case. Good idea to use these restoration diodes there? Thanks. -- Best regards, Chris mailto:dead.fets@gmail.com